List of Ben 10 villains

Vilgax

Voiced by:

• Steven Blum - Ben 10 and Ben 10: Omniverse
• James Remar - Ben 10: Alien Force and Ben 10: Ultimate Alien
• John DiMaggio - Ben 10 Alien Force: Vilgax Attacks and Ben 10: Galactic Racing
• Yuri Lowenthal - Ben 10 (Reboot)

Vilgax is a warlord who is Ben's first and most recurring nemesis through the series. Being of the Chimera Sui Generis race, who can turn into giant squid-like creatures when exposed to water, Vilgax was exiled from his home world for being ruthless, cruel, and power hungry. Soon after, Vilgax meets Maltruant as depicted in the Omniverse series finale which had him indirectly learn of the Omnitrix's existence when attacked by George Washington and a mysterious figure later revealed to be Ben. Since witnessing it, and after it is built years later, Vilgax became determined to have the Omnitrix and use it to build an army capable of conquering every planet in the galaxy. Other than that, establishing Vilgaxia as the center of his personal empire, Vilgax made himself infamously feared to the point of using Bioroids as his minions. But despite his cruel and villainous tendencies, Vilgax does care for his subjects' wellbeing and would do anything for their safety. Vilgax is also a self-proclaimed master of the Omnitrix, as he claimed that unlocking the Omnitrix's master control function was "child's play" for him, though Ben later learned to change Omnitrix's code sequence by the events of Alien Force.

In the beginning of the original series, Vilgax's attempt to get the Omnitrix from Xylene resulted with his body damaged and undergoing cybernetic enhancement while recuperating while he sent his robots and bounty hunters to find the item. Once his body is healed, with the added ability to increase his muscle mass, Vilgax began to go after Ben numerous times. Vilgax returns years later in the Ben 10: Alien Force episode "Vengeance of Vilgax", having conquered ten planets in order to take the powers and weapons of the champions from the conquered worlds as his own. His new abilities include even greater strength and invulnerability, a red laser projector, wind breath, flight at light-speed, super-hearing, a large sword he can cover with flame or Taydenite, and a gauntlet he can use to generate force fields and electric shocks. After taking Ultimos' powers while conquering his tenth planet, Vilgax arrives on Earth to challenge Ben. Instead, Vilgax ends up facing Max and the Plumber Helpers before Ben arrives and defeats him as Diamondhead. Though intergalactic law dictates him to leave Earth and never return, Vilgax continued to return to Earth a few more times to get his revenge.

In the Alien Force series finale "The Final Battle", Vilgax teams up with Albedo in order to take the Omnitrix. When Albedo gets Ben to surrender the Omnitrix, Vilgax goes back on his deal and imprisons Albedo while revealing his plan to have the Omnitrix power his robots. But the plan is foiled when Ben activates the Omnitrix's self-destruct to render Vilgax's robots useless and then uses the Ultimatrix to fight Vilgax as his ship crashes into the sea. This causes Vilgax to assume his squid form and attempt to eat Ben before he escapes the sinking ship before it explodes. As Ben expected, making his return in Ben 10: Ultimate Alien, Vilgax survived the destruction of his ship before he is rendered too weak to return to his usual form. Vilgax was eventually found by the Flame Keeper's Circle, believing the intergalactic conqueror to be Diagon due to his cephalopodic appearance as he uses the cult to achieve a means to leave Earth and rebuild his empire. Despite Ben's attempt to expose Vilgax in "The Flame Keeper's Circle", the cult refused to accept the truth until Vilgax regains his usual form obtaining the sword of Ascalon and Diagon's heart in "A Knight to Remember", Vilgax reveals himself once obtaining both the sword of Ascalon and Diagon's heart.

However, deceived by Diagon with the promise of more power, Vilgax cracks the seal that kept Diagon out of reality and is sucked into the other side. There, witnessing its power firsthand, Vilgax seems to willingly become Diagon's servant and is physically altered with Lucubra features and is given new powers. By the events of "The Beginning of the End" and "The Ultimate Enemy", Vilgax returns to reality as a herald of Diagon to fully destroy the seal. However, after Diagon is freed and George killed, Vilgax reveals his true scheme to take Diagon's powers for his own. Battling Ben, Vilgax loses his newly gained power while stabbed with Ascalon, returning to his original state as he attempts to talk Ben into giving into allure of the power he currently has. But his manipulation fails as Ben manages to remain in control and restore everyone on Earth to normal with Vilgax taken into Plumber custody soon after.

Returning in Ben 10: Omnniverse, with aspects of his design in the original series, Vilgax was being escorted to a prison planet during the events of "Vilgax Must Croak" before an Incursion attack enabled him to escape. Vilgax's whereabouts since then are a mystery though a hologram of him appeared in "Bengeance Is Mine". It is eventually revealed by the "And Then There Was None"/"And Then There Was Ben" two-part episode that Vilgax allied himself with Eon and Albedo to recruit evil incarnations of Ben across the multiverse. However, upon reaching a universe where the Omnitrix never existed, Vilgax changed his plans and uses a Chronosapien bomb that he received from Maltruant from the events of the Omniverse series finale to wipe all non residential Bens. However, Ben gives the Omnitrix to the alternate universe's version of himself to restore the Ben 10 multiverse and then undo Vilgax's action. This leads to Vilgax's defeat and imprisonment by the alternate universe's Plumbers, though he subsequently returned to his home universe and joined forces with Albedo to attack Ben using armor made from Malware. However, Vilgax is defeated and trapped in the calcified armor as his ship explodes and the remains of Malware emerge from his cracks.

Vilgax appears in the rebooted episode "Omni-Tricked Part 3". Originally, he appears before Ben as Vil, a shriveled up old Chimera Sui Generis, and the genetic donor of Gax. Vil teaches Ben how to use Gax's abilities, earning his trust so he can take back his genetic sample and regain his youthful appearance. After doing so, Vilgax proceeds to thrash Ben and the newly arrived Kraab, Sixsix, and Tetrax (who in this continuity are a part of an organization to prevent Vilgax's return). In "Omni-Trcked Part 4," Vilgax attacks a local volcano to siphon off the volcanic energy to escape Earth. Ben ultimately defeats Vilgax by using Upgrade to send his ship into the lava and supercharge the Omnitrix, temporarily giving him a Master Control like boost. He later returns in "Out to Launch" where he hijacks an experimental space shuttle, and in "Animorphosis" where he briefly allies himself with Dr. Animo.

In "The 11th Alien", Vilgax attempts to convince alien that his possession of the Omnitrix-and particularly the newly unlocked alien Shock Rock-is a danger to the Earth. To accomplished this, he recruits the Weatherheads to use their powers to make it seem as though the watch's energies are affecting Earth's environment. His plan is thwarted after the Weatherheads realize he had no intention of honoring their agreement, and Ben is able to pit them against each other. He later forms an alliance with Zombozo in "Super-Villain Team-Up."

Doctor Animo

Voiced by:

• Dwight Schultz - Ben 10, Ben 10: Alien Force, Ben 10: Ultimate Alien, Ben 10: Omniverse and Ben 10 (Reboot)

Dr. Aloysius James Animo is a brilliant mad scientist obsessed with genetic experiments on animals, and Ben's first human enemy. He was once a promising researcher in veterinary science, but his career was cut short when he was discovered to be performing twisted genetic experiments on animals. He had hoped that his research would win him the Verties Award, an award in veterinary science, but the revelation resulted with the award given to another doctor named Kelly. This drove Animo insane as he dropped off the map for five years until he could perfect his research.

Before his first appearance in the show, Dr. Animo watched a TV report showing Ben as Diamondhead and got inspired to build the "Transmodulator", a device that can mutate animals into giant monsters and bring back dead creatures such as a wax statue of a woolly mammoth and a Tyrannosaurus skeleton. He attempted to use his new monsters to take his revenge against Kelly and take his prize, but he was stopped by Ben. After this, he became one of the most recurrent villains in the show, usually trying to create armies of mutant monsters, and was even able to use DNA information from the Omnitrix to enhance his creatures twice. In "Secret of the Omnitrix", having learned this ability from Clancy while they were members of the Negative 10, Animo devised a means to telepathically control creatures of lesser intelligence. Ben also encountered a future version of Animo during the events of "Ben 10,000", the scientist's head transplanted onto a cybernetic albino gorilla body after an unfortunate accident.

Returning in Ben 10: Alien Force, having ended up in the Null Void while becoming more muscular and less green. In Voided, Animo conquered the dimension under the alias of D'Void and then forced the residents of the Null Void to build a machine which would open a portal to Earth so he could conquer it while enhancing his physical attributes, but he was stopped by the combined forces of Ben and the resistance founded by Max and the Plumber's helpers. Returning to old mofit, Animo returns in Ben 10: Ultimate Alien in "Escape From Aggregor" as he uses a mind-control headband to force a Yeti to fight Ben as part of a diversion as part of his scheme to turn anyone within the vicinity of the Himalayas into Yetis before it was foiled. In the aftermath of "It's Not Easy Being Gwen", after using mutant frogs to attack the city, Dr. Animo is sent to jail. However, in "The Eggman Cometh," Animo abuses the justice system to be put on parole and uses a chicken farm as a front to create Pterodactyl Men from the chicken eggs. Ben manages to thwart him again by using Jury Rigg to convert Animo's machine into an evolution ray to evolve the Pterodactyl Men into chickens and also made a local sheriff super-smart.

As revealed in Ben 10: Omniverse, Animo ended up in a Plumber prison cell which he decorated with patchwork animal dolls. Making his reintroduction in "It Was Them", Animo escaped and attempted to enlarge Earth's ant population and take over the world. However, due to Ben’s interference, Animo's plan was foiled and he was returned to his cell. Dr. Animo eventually escapes his prison and resurrects V.V. Argost during the events of "T.G.I.S." to enact a scheme to conquer the world with "Franken-Cryptids" while aiding V.V. Argost in getting his revenge on the Saturday family. But the scheme ends with Animo chased off by the Chupacabras he used to revive Argost. Animo is later briefly freed by his future incarnation during the events of "Animo Crackers", receiving a new set of antenna that double as a mutation device. The future Animo ends up being defeated and brought back to his timezone to be placed in a Plumber cell during the first half of the series finale.

Animo also appears in the reboot series, in which his creations are divided into two groups: arrogant "Alphas" and good-natured "Accidentals", with the former despising the latter. Animo also appears in "The Beast Inside", in which it is revealed that his father was a veterinarian named Apotheosis Animo. Animo and his father were close, and Ben and Gwen use this information to reach him after a transformation process Animo created is inadvertently turned against him. The Animerger device he developed was intended to mutate humans using animal DNA, but the process is reversed when the subject's human side is revived by a powerful sentimental emotional response and mutates into a wolf-octopus hybrid when Heatblast explodes it. He also appears in "Animorphosis" where he briefly teams up with Vilgax but is later betrayed by the alien, and briefly transforms into Rath after injecting himself with DNA extracted from the Omnitrix.

In "Can I Keep It?", Animo creates a mutant called the Cadobbit, which worms it's way into Ben's affections in order to destroy him when his guard is down. In "Chicken Nuggets of Wisdom" Animo briefly contemplates giving up on supervillainy until he comes under attack-or so he thinks-from Ben, prompting him to attack the Tennysons with a bat-like mutant and a ray that turns Max into a chicken.

Sixsix

Voiced by:

• Dee Bradley Baker - Ben 10 and Ben 10: Omniverse
• Josh Keaton - Ben 10 (Reboot)

Sixsix (named after the caliber of the two pistols that he wields) is a bounty hunter and mercenary from the Sotoragg system. Unlike the villains Ben has faced, Sixsix and his race speak in language that only some aliens can understand him. It is said he has quite a reputation, as he wears a disguise when in Incarcecon as a means to avoid be attacked by those trying to prove their prowess by beating him.

Sixsix has purple armor and strange, clamp-like feet; the armor he wears was taken from an assassin droid he gutted. He is equipped with a jetpack, and his armor is covered with pouches that hold various weapons and projectiles, such as twin blasters, laser discs, an energized buzz saw, laser blade and whip, a sonic weapon, throwing pikes, grenades, bolas, rockets, and several tentacle-mounted lasers coming out of his back pack. He also has several very strange small claws and hands that extend from his shoulders that are usually used to throw the small pikes coming out of his jet pack, or bombs when he is using his blasters.

He was added to the original series, first appearing in the episode "Hunted", being recruited by Vilgax with Kraab and Tetrax to get the Omnitrix. He is defeated by Grey Matter and Tetrax. Returning in "Galactic Enforcers" and forming an alliance with his new colleague Vulkanus, who execute the task of obtaining the Bicenthium Alloy and mix it with the element X to exploit the solar system and take over the galaxy. But they are both defeated by the Galactic enforcers and Cannonbolt. Later in the movie "Ben 10: The Secret of the Omnitrix" it's revealed that after his second confrontation against Ben he was sent to Incarcecon and remained there until the young Tennyson and Tetrax infiltrated the place looking for Azmuth. Sixsix then confronted Tetrax but their fight was interrupted when Ben's Omnitrix sent out a feedback, knocking Sixsix out cold.

Later on Ben 10: Omniverse, Sixsix returns in the episode "Vilgax Must Croak" and was hired along with his brother Sevenseven and sister Eighteight by Attea to execute the mission to kill Vilgax but his plans fail when Ben, Rook and group plumbers prevent it. In "Cough It Up" Sixsix, together with his brother and sister, were recruited by Psyphon to attack again, but they are defeated by Ben, Rook and Spanner.

Sixsix also appears in the Ben 10 reboot, this time teaming up with Kraab and Tetrax in an effort to stop Vilgax from regaining his original power. They attack Ben in "Omni-Tricked" in an effort to prevent this occurrence, but are forced to flee to escape a train heading for a cliff; they later return and try to stop Vilgax after he is restored but fail. In "Bounty Ball" the trio attack Ben again, apparently seeking to capture him for their employer; however, Ben manages to turn them against each other.

Kraab

Voiced by:

• Billy West - Ben 10
• Jeff Bennett - Ben 10: Alien Force
• Dee Bradley Baker - Ben 10: Omniverse
• Travis Willingham - Ben 10 (Reboot)

Kraab was one of the three bounty hunters hired by Vilgax to hunt down the Omnitrix in "Hunted", the others being Sixsix and Tetrax. He defeated Ghostfreak but was defeated when Grey Matter ripped out some wires from his neck, causing his body to go haywire. Kraab reappeared in "The Final Battle: Part 1", hired by an unknown client to hunt down Ben. He was frozen by Big Chill and left aboard the ship. Since Ben couldn't save the ship, the ship exploded, but Gwen and Kevin managed to save Kraab. Kraab returns in "Cough It Up", when Psyphon hires bounty hunters to find him a very precious item. He was first seen on the streets of Undertown, searching for it. Jimmy Jones chased him till the entrance of the Black Hole. Psyphon told the hunters that the item was stolen by someone who poisoned the guards with quills. Kraab detonated one of Argit's office's walls and told Argit to give him the item. Argit was surprised to see him because he thought he was still in jail. Unfortunately for Kraab, Ben, Rook, and Spanner happened to be there too. Ben transformed into Frankenstrike and took out Kraab with one hit. At the end of the episode, he was defeated by Argit's Techadon robots and was banned from Undertown.

Kraab returns in Ben 10 (Reboot), this time as an ally of Sixsix and Tetrax who attempts to prevent Vilgax's return.

Rojo

Voiced by:

• Jennifer Hale - Ben 10 and Ben 10: Omniverse
• Kari Wahlgren - Ben 10: Ultimate Alien

Rojo, originally known as Joey, is the leader of a heavily armed female biker gang, amoral and greedy with no hesitation to attack innocent bystanders if they happen to annoy her. Rojo was first introduced in "The Alliance", on a failed attempt to rob an armored truck. She is thwarted by Four Arms and two of Vilgax's Drones coming after Ben. While looking at one of the damaged drones, Rojo ends up being converted into a cyborg after the remnants merged onto her body. The upgrade gives her the ability to fly, superhuman speed, metallic claws, and a pair of blasters attached to each shoulder. Vilgax was able to communicate with her through the parts and force her to track down the Omnitrix for him. Rojo is turned back to normal when Upgrade shorted-out the spare parts, after which Gwen knocks her unconscious for attempting a sneak attack on Upgrade.

She returns in "Ben 10 vs. the Negative 10", as part of the Negative Ten. She now sports new alien tech and armor that was presumably supplied by the Forever Knights. In that episode she is also shown to have a rivalry with Charmcaster over being the "baddest girl" in the group. In the battle, she interferes with Gwen and Charmcaster's duel but gets kicked away by Charmcaster and Gwen's combined spell power. Later she quarrels with other Negative 10 members and later was trapped in the force field where the sub-energy once resided.

Rojo returned and made a brief appearance in the Ben 10: Ultimate Alien episode "Hit 'Em Where They Live", where she and her biker gang tried to rob a train. She apparently reformed her biker gang and upgraded them, using blue and yellow versions of her new red highlighted suit and riding hover-cycles. They were eventually stopped by Ben, Gwen and Kevin. Rojo later appears in Ben 10: Omniverse when hired by Simian to help him steal from Argit during the events of "The Color of Monkey", only to end up being arrested. She appears as a contestant in "The Most Dangerous Episode", and is sent back to prison at the end of it.

Zombozo

Voiced by:

• John Kassir - Ben 10
• John DiMaggio - Ben 10: Ultimate Alien, Ben 10: Omniverse and Ben 10 (Reboot)

Zombozo (a play on "zombie" and "bozo"), his full name Herbert R. Zomboni, is a cruel and creepy clown mastermind with a dark sense of humor that borders on more sadistic and psychopathic behavior as he thrives on the fear of others. First introduced in "Last Laugh" with a circus as a front, Zombozo stages shows to bring people in and then uses a machine he calls the "Psyclown" to drain the happiness and life energy from them, leaving them depleted and sad or aged while his minions strip the town. He was eventually defeated when Ben overcame his fear of clowns after seeing the effect of Zombozo's device on Max and Gwen, and terrorized Zombozo as Ghostfreak, causing him to literally explode in a burst of confetti out of fright.

He returned in Ben 10: Ultimate Alien episode "Hit 'Em Where They Live", revealing that the "explosion" of confetti was a ruse though the ordeal had weakened him. After Ben's identity was revealed to the world, he and Ben's other old enemies organized attacks against Ben's family to get their revenge. After most of the attacks were stopped by Max, Zombozo formed a team with Charmcaster and Vulkanus as he kidnapped Ben's mother as a hostage to bring Ben, Gwen, and Kevin to his hideout, then separate them and let the members of his team take them down one by one. His plan eventually backfired when he tried to kill Mrs. Tennyson in a slow and cruel way, causing an angry Gwen to assume her dormant Anodite form while threatening an intimidated Zombozo to spread the word to the other villains not to go after their families again.

By the events of Ben 10: Omniverse, he is caught by Ben's group during their last day as a team when he stole a brain from Bellwood's brain bank, Zombozo began to rot at an alarming rate as the result of being starved of fear. However, during the events of "Something Zombozo This Way Comes", Zombozo escapes the Plumbers and reunites the Circus Freak Trio to stage a circus in Bellwood to convert those attending into zombie-clowns to regain his strength through them scaring people, but is defeated by Ben when he became Toepick and is forced to flee.

In the reboot, Zombozo is more cartoonish looking and is relatively unchanged, except that many of his plans involve hypnotizing various victims for his schemes.

Hex

Voiced by:

• Khary Payton – Ben 10, Ben 10: Alien Force, Ben 10: Ultimate Alien and Ben 10: Omniverse
• Kari Wahlgren – Ben 10 (as a child in "Don't Drink the Water")
• Robin Atkin Downes - Ben 10 (Reboot)

Hex is a self-proclaimed "Master Magician" from Legerdomain who desires to rule the world with his unmatched magical mystical powers and the Staff of Ages. In the episode "Tough Luck", it is shown that Hex emotionally and gives the heavy implication that he even physically abuses his niece Charmcaster. By seeing her as a servant who should slavishly obey him at all times rather than a family member, he intimidates her into being submissive and respectful to him, and when she gets out of line or fails him in some way, he turns his magic against her. The abuse has already taken its toll on her and has made her into the apprentice Hex has always wanted her to be; an angry, hateful, ruthless and power-hungry person - like himself.

He possesses five magical mystic charms called the "Charms of Bezel" that give him incredible mystical powers and abilities, in addition to his own spell-casting abilities. It is unknown how he possesses powers even without the charms, but since it is implied in "In Charm's Way" that Charmcaster, daughter of his brother Spellbinder, was trained in controlling and manipulating mana, it was probably the same for him. He first fights the Tennysons while he tries to steal the final Charm of Bezel, during the fight with Ben, Grandpa Max, and Gwen, he locked in a stone casket until the police arrived, later, he was busted out by his niece Charmcaster and attacked Las Vegas for an artifact that can recreate the Charms of Bazel. Though he fought Ben numerous times following his plan failing, Hex targeted Gwen in most of his appearances

Hex returns in the third season of Ben 10: Alien Force, where it is revealed he has seemingly made up with his niece between the two series, and now lives in a tall, Japanese-style mansion where he keeps all his books of magic, including the Archamada. He has returned to his original age, and his look is mostly the same as before, though his clothes are now fully red instead of black and red, and his face is whiter than before, making it look even more like a skull.

In "Time Heals", Gwen sneaked into Hex's mansion to steal a specific spell book in one of her attempts to cure Kevin's mutation. Despite the warning of Paradox, Gwen does so but ended up causing a timeline where Hex has taken over the world, upon evading Charmcaster, Gwen infiltrates Hex's mansion again and runs into Hex who had become aware of the timeline change. While a weakened Ben tries to stop Hex and Charmcaster, Gwen successfully makes off with the spell book and prevents herself from causing this timeline.

He reappears in the Ultimate Alien in episode "The Enemy of My Frenemy". Gwen tries to steal one of his books only for her to be caught by Hex. Gwen tells him about Ledgerdomain where Charmcaster is currently fighting Addwaitya. Although Hex doesn't want to help rescue Charmcaster, he does allow Gwen to take some magical items that she needs in helping Charmcaster. By the events of the Omniverse series, Hex turned over a new leaf and became a professor at the university that Gwen is attending. However, in episode "Charm School", Hex ends up being turned into a totem figurine by Charmcaster with Gwen indirectly inheriting his library and the Staff of Ages. He is restored back to normal in "Third Time's a Charm".

In Omniverse, Hex has gotten over his depression of Charmcaster being in Ledgerdomain. He is now a teacher at Gwen's college, no longer bearing a grudge; he is her favorite teacher. Hex appears in "The Most Dangers Game Show", where the contestants had to sneak through Hex's library as a challenge. Jennifer Nocturne lost the challenge when she hushed Hex back.

Hex returns in the reboot series, though he appears to be less competent; Gwen was able to trick him into throwing away the Wand of Merlin by claiming to possess it and then successfully tricked Hex into believing she had magical abilities. He also appears in "Story Bored" where he steals the Grimoire of Achamada and uses its magic to merge with the monstrous snake king Exus, becoming the Nāga-like Hexus. However, he is defeated after Ben recovers the grimoire, which Gwen then uses to briefly turn him into a mouse before he flees. He also appears in "Freaky Ben-Gwen" in search of the Titan Gaunlets, gloves that grant their wearer super strength and Earth-manipulation abilities. After witnessing Ben and Gwen squabble, he uses a spell to switch their bodies in hopes of stopping them from thwarting him again. Despite this and his obtaining the gloves, he is bested and ends up inadvertently returning the two to normal and losing his spell book, inadvertently leading to the rise of Charmcaster. In "Screamcatcher" Hex uses a magical crystal to draw Ben into a realm of nightmares, but is defeated when Ben takes control of it. In "Creature Feature" Hex is revealed to have been on Earth for centuries, having to periodically renew his powers by creating a light-eating monster to seek out a pool of light to rejuvenate himself in.

Phil

Voiced by:

• Robert Patrick - Ben 10
• Rob Paulsen - Ben 10: Omniverse
• John DiMaggio - Ben 10 (Reboot)

Phil is a former Plumber and Max's partner, continuing to hunt aliens after the Plumbers disbanded years ago. But in reality, using the Null Void projector, Phil scams people into paying him to remove the aliens he sets free. During the events of "Truth", Phil crosses paths with Max and his grandchildren, tempting Ben into remaking the Plumbers. But once his scheme is revealed, Phil releases an alien to deal with Max, but Ben is able to rescue him and eventually trap Phil in the Null Void.

As revealed in the "Of Predators and Prey" 2-part episode of Ben 10: Omniverse, Phil was found a year later by Malware and Dr. Psychobos to be used as a test subject for the Nemetrix. Assuming the form of a Terroranchula, Phil battled Ben and overpowered him. But due to his higher brain functions, Phil was unable to adapt into a feral form and was relieved of the Nemetrix while teleported back to the Null Void after the fight ended. However, making his return on "Max's Monster", the ordeal altered Phil's DNA to give him the ability to become a Terroranchula/human hybrid with the ability to consume energy to maintain his new form.

Soon after his defeat, Phil is recruited by the Rooters as a member of the group, and joins in their plan to destroy Ben; however, the Rooters are then left in the Null Void after the depths of their treachery are discovered by the Plumbers' leader, the Magistrata.

Phil appears in the reboot starting in "Omni-tricked Part 2" as an ally, rather than an enemy. In this continuity, Phil is an electrical engineer who was enlisted after Ben first unlocked Gax and lost the ability to control when he transformed. However, he does seem to have alien knowledge, as he recognized the Omnitrix.

Forever Knights

The Forever Knights is a secret paramilitary organization, a loose reference to the Knights Templar, that deals with the alien encounters and other varying activities. The group was founded by Sir George for the purpose of fighting Dagon, but his departure resulted with the Forever Knights splintered into factions each led by a Forever King. But by the events of "Ultimate Alien", the Forever Knights were reunited under George to combat the Esoterica and Diagon. However, the conflict that ensued killed Sir George and wiped out all the Forever Knights with only a small group under Chadwick remaining (Sir Morton, Red Knight, and the Twin Knights). Chadwick led the remaining Forever Knights into resuming their role in eliminating all alien life from Earth.

In all three TV series and one video game, different VAs have voiced the Forever Knight soldiers: Dee Bradley Baker, Jeff Bennett, Greg Cipes, Tim Curry, John DiMaggio, Greg Ellis, Robert David Hall, Yuri Lowenthal, Peter MacNicol, Richard McGonagle, Scott Menville, Rob Paulsen, Khary Payton, Kevin Michael Richardson, and Fred Tatasciore.

Clancy

Voiced by:

• Nicholas Guest - Ben 10

Clancy is a green-skinned homeless man who has the ability to psychically control any type of insect or arachnid, using first-person plural pronouns like "we" in his sentences. When Councilwoman Liang attempts to redevelop her city, Clancy learns that the condemned house he is residing in is to be torn down and resolves to feed her to his insects. However, Ben intervenes as Fourarms and the Clancy's home is destroyed. When his later plan to nuke the town out of revenge is ruined, Clancy decides to take revenge against the Tennysons instead. Luckily, Grandpa Max's San Ju Yen Pien medicine overrides Clancy's powers as the outcast is knocked out. By the time he resurfaces as a member of the Negative 10, Clancy mutated into an insectoid creature with help from the Forever Knights with a new ability where he can emit wasps from his mouth.

Vulkanus

Voiced by:

• John DiMaggio - Ben 10, Ben 10: Alien Force, Ben 10: Ultimate Alien and Ben 10: Omniverse

Vulkanus is a Detrovite in mechanical armor who first appeared in first series episode "The Galactic Enforcers" where he partnered up with Sixsix in order to build a weapon capable of destroying a solar system using the "element X" and Bicenthium Alloy. As revealed in the Omniverse episode "The Ballad of Mr. Baumann", Vulkanus's attempt to retrieve a vial of element X resulted with his body destroyed from the neck down. Vulkanus since wears a special regeneration suit that would eventually restore his body, which looks diminutive by the events of the sequel series.

Vulkanus returns in the Ben 10: Alien Force episode "Kevin's Big Score", where according him, Kevin betrayed Vulkanus during a "counterfeit isotope" scam a few years earlier. Kevin left him holding the merchandise when The Plumbers arrived, and though he managed to escape, the Plumbers destroyed his ship, making unable to leave Earth; so he resorted to trading level three alien technology to get by. When Kevin arrives looking to obtain an important item, which was a holo-viewer from Max, Vulkanus decides to get back at him for the betrayal by forcing Kevin to absorb a small piece of "Taedenite", the hardest and rarest gem in the galaxy; this caused Kevin's body to mass-produce the gem, thus giving Vulkanus an endless supply. But Vulkanus's scheme is foiled by Ben after he uses Big Chill to freeze off Vulkanus's regeneration suit. Rather than attempt to arrest him, however, Kevin leaves Vulkanus with the small fortune in crystals he had managed to chip off beforehand, considering it as payment for his past actions. But Volcanus then used his new fortune to buy permission to change Earth climate so it would be more like his home world, but again was stopped by Ben. In Con of Rath he and his minions hide in a strange planet with a Taedenite, when Ben in Rath and teams arrived in the place he orders kill them but Ben defeats with a ground stroke.

Vulkanus later returns in the Ben 10: Ultimate Alien episode "Hit 'Em Where They Live", he teamed up with Zombozo and Charmcaster to attack Ben's loved ones. In "Greetings from Techadon", he buys a Technodon Robot manufacture factory programmed to destroy Ben, each destroyed robot providing data for the next robot with counters to Ben's alien forms. However, as the Technodon robots are programmed to target anything with an Omnitrix symbol on it, it was a simple task for Ben to hide the Ultimatrix from sight while a fake is placed on Vulkanus.

In the Ben 10: Omniverse episode "Special Delivery", Vulkanus is among those who assist Psyphon into claiming the Dwarfstar from Ben. He later appears in the episode "The Ballad of Mr. Baumann" to obtain the elemental X vial that cost him his body years ago.

Charmcaster

Voiced by:

• Kari Wahlgren - Ben 10, Ben 10: Alien Force, Ben 10: Ultimate Alien and Ben 10: Omniverse
• Tara Strong - Ben 10 (2016 series)

Hope is Hex's teenage niece who operates under the name Charmcaster. Like him, she originated from Ledgerdomain (or Yahwahtacsip) and was the daughter of Spellbinder. She carries a magic satchel from which she can draw all manner of items, such as magical explosives, throwing blades, or even various clay animals to enlarge and animate. Although small, the bag seems to have something of a pocket dimension inside. She is also skilled in various magical spells, although it's clear that because of her inexperience, she is not as powerful as her uncle. She is often the victim of emotionally based abuse at the hands of her uncle and it is also heavily implied he abuses her even physically. This abuse strongly explains her egocentric and adversarial nature with the Tennyson family, especially Gwen, although like Kevin she becomes more of an anti-hero and occasional ally to the Tennysons as time goes on.

Forced to flee to Earth when her father died at the hands of Adwaita, Charmcaster resolved to become a great sorceress so she can have her revenge. During her introduction in "Tough Luck", she helped her uncle out of jail to get the Charm of Bezel, and is ultimately defeated by Gwen. Charmcaster officially became the girl's nemesis in "A Change of Face" after a failed attempt with body swap spell causes her to lose her spell book to Gwen while she is trapped in a females' juvenile hall. Charmcaster later was part of the Negative 10's plot to defeat Ben, though more concerned in defeating Gwen rather than Ben, and also had a rivalry with her partner Rojo.

Charmcaster returns in Ben 10: Alien Force, living with her uncle. She wears a way different outfit, utilizing mana manipulation in her various spells, and far more vicious, sadistic, and arrogant than before. During the events of "In Charm's Way", Charmcaster tricks Kevin into attacking Ben by promising to restore him to normal, for she can drain Gwen's magical and Anodite powers. She and Hex conquer the world in the alternate timeline of "Time Heals".

In the Ben 10: Ultimate Alien episode "Hit 'Em Where They Live", Charmcaster teamed up with Zombozo and Vulkanus in a plot to kidnap Ben's parents.

During the events of "Where the Magic Happens", Charmcaster helps Ben, Gwen and Kevin to get in Ledgerdomain so they can find a piece of the Map of Infinity. During that time, Charmcaster's background story is revealed as she moves past her feelings of resentment toward Gwen and actually develops a friendship with her. This change in her spurred her to buy time for Ben's group to escape while she remained behind in Ledgerdomain with the hopes of defeating a powerless Adwaita at last.

By the events of "The Enemy of My Frenemy", Charmcaster reclaimed Ledgerdomain during the power vacuum left by Adwaita's defeat and becomes corrupted with power, building a device that drains the lives of living things to sacrifice all life on her domain to being Spellbinder back to life. Ben, Gwen, and Kevin attempted to stop her before they end up being sacrificed as well. But the revived Spellbinder, learning of the horror his daughter committed for his sake, reverses the ceremony to restore everyones' lives back while a saddened Charmaster is left with how she should spend her life now. Gwen, pitying her and hoping she can get better, leaves Charmcaster in charge of Ledgerdomain rather than apprehending her. In "Couples Retreat", Charmcaster attempted to fill the void in her life with Darkstar, thinking he loved her while unaware that he is using her for her powers. When Ben's group arrive to Ledgerdomain after him, Charmcaster overheard Darkstar's history with Gwen, attacking her before learning of what kind of person he really is. Reluctant to accept the truth, Charmcaster accepts it when he is unable to remember her real name. Furious, Charmcaster expels Darkstar from Ledgerdomain and leaves him both powerless and at the mercy of Ben's group. Charmcaster stands alone in the ruins of her castle sadly and tearfully gazing at Michael's mask that was left behind, heartbroken at being betrayed by the first person she felt love and affection for.

By events of Ben 10: Omniverse, Charmcaster appeared to have gone insane and unhinged since it appeared she was now constantly talking to her satchel. In actuality, she was speaking to the totem figurine that Adwaita became. While Charmcaster made a cameo appearance in "Mystery Incorporeal" where she tortured a defenseless Darkstar out of revenge prior to turning him into a figurine, she makes her official return in "Charmed, I'm Sure", Charmcaster appeared on Anur Transyl and used Ben and his group to recover the Alpha Rune that Zs'Skayr stole from her. Charmcaster later returns in "Charm School" where she turns her uncle Hex into a figurine to access his library and claim the Staff of Ages as her birthright. But Gwen's interference forces Charmcaster back to Ledgerdomain. In "Third Time's a Charm", after capturing Gwen and achieving her goal to be the most powerful magic user, Charmcaster is tricked into transforming herself into a stone totem figurine. She is left seen kept in her own bag in Gwen's room until she can learn the error of her ways, with Gwen expressing hope that the two of them can become friends someday. According to Man of Action member Duncan Rouleau, this would ultimately happen and potentially shown if Gwen ever received a spin-off.

In "The Most Dangerous Game Show", Charmcaster appears as a contestant on "The Most Dangerous Game Show" hosted by Charles Xenith.

Charmcaster reappears in the reboot, but is radically altered. While her main color scheme of purple clothing and white hair remains unchanged, her general appearance as far more punk/goth based, wearing a choker and spiked headband. She is revealed to be a fan of Michael Morningstar, and her powers are also shown to be quite different as well, using Hex's magic book for varying attacks including animation, teleportation, and using the pages to allow her to float and trap people within the book as drawings. Her past is revealed in her introductory episode "The Charm Offensive": she was initially an insecure, nerdy girl named Heather, but stumbled upon Hex's magic book (which he had lost in "Freaky Ben Gwen"), altering her appearance and making her far more confident and rebellious. She found Michael Morningstar being defeated by Ben in "Bright Lights, Black Hearts," where both decided to work to achieve revenge against Ben. Throughout "The Charm Offensive," Morningstar acts highly abusive to her, fluctuating between treating her with adoration, to demeaning her and even taking away her energy without her consent, showing that while she had indeed become more confident, her insecurity issues were still there. It is only when Gwen shows that he does not care for her that Charmcaster rebels against him, trapping him in Hex's book, but wanting to prove herself better than Gwen, she swears the next time they meet, they will be fighting.

Zs'Skayr

Voiced by:

• Steven Blum - Ben 10 and Ben 10 Omniverse
• Jeff Bennett - Ben 10: Alien Force

He was dubbed Ghostfreak by Ben since he is the human's Ectonurite form yet is actually a clone of the form's donor Zs'Skayr (a play on "The Scare"). Originally High Ectonurite, Zs'Skayr learned about the Omnitrix from reading one of Vilgax's data, tricking Myaxx into allowing him to accompany her in acquiring a sample of Florauna DNA. However, possessing the donor, Zs'Skayr manages to have his DNA scanned with the Florauna's for the Omnitrix. While the original Zs'Skayr died sometime between then and the original series, he lived through the genetic clone manifested within the Omnitrix. Ghostfreak's original appearance was similar to that of a ghost with a black track along his skin but after freeing himself, he tore off the protective second skin to reveal Zs'Skayr's true form. He has the power to phase through matter and possess other life forms. He can also become far stronger if he's in complete darkness, which allows him to become even scarier in appearance and fire a powerful energy beam from his chest. However, without the second skin protecting him, sunlight can cause him to combust and die.

Only able to influence Ben originally as Ghostfreak when the boy first used the form before regaining his strength, Zs'Skayr finally managed to force his way out of the Omnitrix in the episode "Ghostfreaked Out". After peeling off the protective layer of skin that normally covered him, he tried to take over Ben's body in order to become whole again. After a failed attempt to possess Ben, he coerced the Circus Freak Trio to help him by taking over Thumbskull and tossing him about the room in a show of force, he was destroyed when he was exposed to sunlight by Ben. However, during the events of "The Return" and "Be Afraid of the Dark", Zs'Skayr is brought back by Viktor and their group of Anur Transylians to enact a master plan to plunge the Earth into darkness so Zs'Skayr can exist in eternal darkness with the Omnitrix as a bonus. But Zs'Skayr is once again defeated by Ben when exposed to sunlight while in space, though he managed to get some of his DNA scanned into Ben's Omnitrix at the last second. As revealed in the Omniverse episode "From Hedorium to Eternity", Zs'Skayr is revealed to have survived and attempted to repeat his scheme to plunge Earth in darkness with the aid of his Ectonurite kin before being sucked into the portal he built.

Zs'Skayr turns up alive in the Ben 10: Alien Force episode "Ghost Town". After being removed from the Codon Stream, Zs'Skayr had apparently been imprisoned by the Galvans; Vilgax frees him on the condition that he tell him the secrets of the Omnitrix and the knowledge to defeat Ben, but Zs'Skayr betrays him and takes over Vilgax's home planet of Vilgaxia, possessing the citizens and turning them into his minions that resemble his sun shielded form. Vilgax then enlists the help of Ben to try to take Vilgaxia back. During the battle, Ben lets Zs'Skayr enter his body, returning the Ectonurite DNA to the Codon Stream, Ben transforms into Ghostfreak but he takes control of him in the same way he turns the Chimera Sui Generis citizens and soon he tries to possess Vilgax, but is defeated by Vilgax and Ben changes back, with Ghostfreak still inside the Omnitrix until the Zs'Skayr persona ended up in Ledgerdomain.

However, in the ending scene of "Mystery Incorporeal", Zs'Skayr emerges from the portal to Ledgerdomain that Darkstar had opened earlier. Weakened, Zs'Skayr resolves to use the Plumbers to ensure his return to Anur Transyl while removing King Xarion from Doctor Viktor's body. Zs'Skayr also formed an alliance with Crujo and Kuphulu. Once back on Anur Transyl, formally introducing himself to Ben by his true nature, Zs'Skayr regains his full strength while readjusting his skull to assume a grim reaper-like appearance and revealing his goal to regain his former title by using the energies of the Alpha Rune he stole from Charmcaster to revive the Vladat race starting with Lord Transyl and use their power to rule the universe. However, Zs'Skayr is defeated by Ben using his Atomix form to create an energy sphere that vaporizes him with Ben keeping the item in Zs'Skayr's castle to discourage any chance of revival.

Exo-Skull

Voiced by:

• Richard McGonagle - Ben 10
• David Kaye - Ben 10: Omniverse

Exo-Skull is a cybernetically enhanced rhinoceros mutant who first appears in Ben's future timeline as seen in "Ben 10,000" as one of Animo's followers.

In the Omniverse series, having an affair with the Merlinisapien Subdora, Exo-Skull is hired by Maltruant to steal the Key to Time for him during the events of "Fight in the Museum". He returns in It's a Mad, Mad, Mad World Ben: Part 1 along with Subdora to help Maltruant again.

Kane North

Voiced by:

• John Cygan - Ben 10
• Corey Burton - Ben 10: Omniverse

Kane North is a TV actor who is the twin brother of Abel North, having framed his brother for stealing his idea for the "Kangaroo Kommando" series that was Ben's favorite show. Kane also had a grudge against Tim Dean for stealing his ideal for the "Super Alien Hero Buddies" show, which was inspired by Ben's adventures.

As revealed in the Omniverse episode "The Vengers", Kane ended up in jail for five years before being released as he once more masquerades as Kangaroo Kommando while teaming up with Billy Billions and Carl Nesmith in a scheme to depose Ben as the hero.

Lt. Steel

Voiced by:

• Michael Gough - Ben 10
• Yuri Lowenthal - Ben 10: Omniverse

Lt. Steel is the leader of SECT, a government task force that deals with alien activity on Earth. He initially perceives Ben and all aliens as a menace due to the actions of a transformed Kevin 11. He later briefly reappears in Omniverse where he and the rest of SECT are attacked by both past and future Animos, requiring Ben to rescue them as Gutrot.

Sublimino

Voiced by:

• Richard Steven Horvitz

Sublimino is a hypnotist who hypnotizes anyone to commit crimes in their dream state.

Highbreed

The race of Atasians, calling themselves the Highbreed, are xenophobic alien races from the planet Augstaka. The Highbreed are very strong, they have wings that let them fly and also shoot claw darts from their hands. They can open their chest up, revealing root-like tentacles they can use to drink water from the ground. They have difficulty surviving and operating in warmer climates, which cause them to quickly dehydrate if they do not find water. They are fiercely loyal to their commander and follow a strict honor code.

They considered themselves as the highest life-form in the universe, due to the Highbreed believing that their DNA is the purest of all alien species and being one of the first forms of life. This idea of racial purity ultimately become their undoing due to a lack of genetic diversity and inbreeding leading to multiple infections and sterility. With their own extinction assured, the Highbreed refused to die alone and spurred their xenocidal rampage throughout the universe to extreme levels to cleanse the universe of "lower life forms". To achieve this, they sent advance forces of Highbreed commanders and Xenocytes to secretly build massive teleporter gates so that the main Highbreed armada arrives and destroy the planet.

In "War of the Worlds" two parter, when the Highbreed begin the final phases of their attack on Earth, Ben used the Omnitrix to reconstruct the DNA of all Highbreed with the DNA of the aliens in the Codon Stream. At first the Highbreed were shocked at losing the genetic consistency that had been a pillar of their cultural identity. Their council immediately considered committing mass suicide as their only remaining honorable route. Luckily, Reinrassic III convinces his people that Ben helped them live again, and is named the new Highbreed Supreme with the war ended.

Different voice actors have voiced the Highbreed: Dee Bradley Baker, Paul Eiding, Richard McGonagle, and Kevin Michael Richardson.

DNAliens

DNAliens are alien races who were infected by Xenocytes, alien leeches artificially mass-produced by the Highbreed that attached to a host. Once attached, the Xenocytes alter their hosts' minds while gradually fusing onto them to transform the hosts into DNAliens. Serving the Highbreed as sacrificial drones, the DNAliens share their masters' speciesist ideals. They thrive on cold weather, so fire damages them beyond repair. Throughout the Ben 10 Alien Force series, Ben and his friends encountered DNAliens created from human hosts. As a result of its user being human, the Omnitrix can undo the process as the Codon Stream recognizes the Xenocytes as non-sapient.

The Xenocytes and the DNAliens returned in Ben 10: Ultimate Alien episode "Simian Says", when the Arachnichimp mercenary Simian stole a Xenocyte Queen and sold it to a crime lord on his homeworld named Mizaru. When he released the Xenocyte, it infected him and began spreading more Xenocytes throughout all of Aranhaschimmia. A twist in this was that Mizaru actually gained control of the Xenocyte Queen which latched onto his head. Eunice, with the help of Simian and Ben's team, were able to reverse the effect and cure all the Arachnachimps while killing the queen.

In the Ben 10: Omniverse episode "Special Delivery", only one see in Ben`s flashback is defeat by Ben in Big Chill.

Different voice actors has voiced and provided the vocal effects for the DNAliens: Dee Bradley Baker, Jeff Bennett, Greg Cipes, Diane Delano, Paul Eiding, Will Friedle, Wallace Langham, and Richard McGonagle.

Gorvan

• John DiMaggio - Ben 10: Alien Force
• Rob Paulsen - Ben 10: Omniverse

Gorvan is a Tetramand who first appeared in Ben 10: Alien Force.

His first television appearance is a cameo in the Omniverse episode "Special Delivery" where he appears at an auction psyohon to receive the Dwarf Star. In "Mud is Thicker than Water", he collaborates with Psyphon and his thugs to infiltrate a Plumber base and steal the Anihilarg. He is defeated by Ben and Gwen. In "CatFight," He is seen along with other Tetramand warriors trying to defeat Looma to claim their right to the throne.

Argit

Voiced by:

• Alexander Polinsky - Ben 10: Alien Force, Ben 10: Ultimate Alien and Ben 10: Omniverse

Argit is a rat-like alien with sleep inducing quills who was originally one of the captive donors in the Rooters' experiments, serving as the genetic donor for Pierce Wheels's abilities. Having befriended Kevin, Argit became an associate after their memories of the Rooters were wiped out. Argit is a known con-artist who out of make money for his own gain or to pay off his debts, even if it means selling out his friends as once admitted to sold off his own mother. (Kevin even backs this up, saying Argit got top dollar for her.)

Argit first appears in Alien Force episode, "Kevin's Big Score", wearing a brown jacket, black shirt, blue jeans and goes about barefoot, making a deal with Kevin and stealing the Rustbucket from him for a profit and making reoccurring appearances. He reappears in Ultimate Alien episode, "Andreas' Fault", where he destroys the Forever Knights' castles with the help of Andreas. Though he seemed to care for Andreas, he shamelessly took advantage over the Talpaedan's innocence and expressed no remorse over his presumed death to Kevin's disgust. In "Enemy of my Enemy", Argit took advantage of him being targeted by Ultimate Kevin to carry out a job by Pa Vreedle to make sure his sons congratulate from the Plumber academy. Though he succeeded, and surviving Kevin, he was arrested soon after. Argit later appeared in "The Purge" and "Greetings from Techadon".

In Omniverse, wearing an orange zipped up jacket with matching pants, Argit is now opossum-like with shorter quills and longer ears. Argit's appearances in the first half range from obtaining the Annihilarg doomsday device for Milleous with disastrous results that were negated and selling out Kevin to Princess Looma. But in "The Frogs of War" two-part, helping Gwen and Kevin in their resistance against the Incurseans, Argit ends up becoming a respectable member of Undertown society despite his kleptomania. In "The Rooters of All Evil" and the "Weapon XI" two-part episode, after Kevin restored his memories, Argit reluctantly accompanied the group in their confrontation with the Rooters. In the series finale, it is revealed that Argit ends up becoming the president of Earth in the future.

Darkstar

Voiced by:

• Wil Wheaton - Ben 10: Alien Force, Ben 10: Ultimate Alien and Ben 10: Omniverse
• Drake Bell - Ben 10 (Reboot)
• Yuri Lowenthal - Ben 10 (Reboot)

Michael Murphy "Mike" Morningstar is the son of a Plumber, initially depicted as a well-mannered individual from an upper-class family and a menagerie of Plumber technology. However, he shows a very uncaring attitude to others around him. Furthermore, he is a vampire-like being, his abilities allow him to absorb energy of another living being to gain the ability to project energy bolts, fly, superhuman strength and stamina, and healthier-looking skin. His victims, on the hand, become zombie-like and loyal to him. Morningstar's powers are a vicious cycle: gaining more power from the mass of life force energy he drains yet it increases his hunger for more. When Morningstar's activities were found out by Ben's group, he pretended to help the group get to the bottom of it and wins the Tennysons' trust, especially Gwen's. Once revealing himself to be the cause for the zombified schoolgirls, draining Gwen's energy to become near invincible, Morningstar overwhelms Ben and Kevin before Gwen managed to take her energy back from him. This leaves Morningstar weakened as his zombie victims followed suit, reducing him to being almost desiccated and powerless.

As a result, Morningstar's face is permanently zombified as he dons a metal helmet as a mask and now calls himself Darkstar, his powers having gradually returned much stronger and gaining new abilities to manipulate dark energy to absorb life force and shoot powerful blasts. In "Darkstar Rising", Darkstar decided to get revenge by getting Ben's group arrested by Magister Prior Gilhil for impersonating Plumbers and by making a deal with a Highbreed that he defeated. When the Highbreed did his part of the deal, Darkstar tried to absorb Ben, Gwen, Kevin, the Highbreed and Gilhil's life force energy but he was unable to absorb Gwen's because she escaped. He later captured Ben, Kevin, the Highbreed, and Ghilhil and was about to absorb all of their life force energy when Gwen came in with a group of DNAliens in which he was unable to absorb all of them because of fatigue. He was defeated by Ben and he was arrested by Magister Ghilhil, being thrown to the Null Void. He was later released by Cooper to help Ben and his team with the Highbreed Invasion. After the Highbreed were defeated, he escaped. Darkstar later resurfaces, and manipulates Kevin, who at the time was dealing with his Omnitrix-induced deformity, into helping him get the Dominus Librium so it can solve their mutual issues during the events of "Trade Off". But once Kevin realizes the danger he caused, he reverses the process with the slab destroyed and Darkstar rendered powerless as he runs off while swearing revenge.

Darkstar later resurfaces in the Ben 10: Ultimate Alien two-part episode "Absolute Power", having been forced to feed off the energy of stray animals just to survive while not attracting attention. Found by Gwen with an offer to help her save Kevin, his face restored as payment, Darkstar reveals that he kept a surviving fragment of the Dominus Librium which needs to strong energy surge would make it usable again. Though Darkstar plotted to use the situation to absorb Ultimate Kevin's acquired energies to become all powerful, Ben anticipated this plot and had Cooper create a mechanism in the machine to revert the process of the absorption and send the energy back to its proper owners. Afterwards, Kevin punches Darkstar in retaliation for their last meeting. Darkstar reappeared in "Couples Retreat", his face now zombified again as he attempted to enter Ledger Domain to acquire its mana. As a result, he tricked Charmcaster in thinking he has romantic feelings for her to be infused with mana. When Ben, Gwen and Kevin got in Ledger Domain, Charmcaster learns of what kind of person Darkstar truly is before exiling him from her realm while leaving him powerless and at the mercy of Ben's group.

Having made a cameo in Ben 10: Omniverse episode "Special Delivery", Darkstar makes his official return in "Mystery Incorporeal", disguised as a nerdy student at Gwen's university named Dante. Revealed that only Ledgerdomain's mana can restore his appearance, using Charmcaster's Stone Creatures and the cult he established, Darkstar captures Gwen and attempts to sacrifice her in a ritual to open a portal to Ledgerdomain and drain its mana. He is defeated by Ben as Ghostfreak, with Gwen placing an anti-magic seal on his forehead to render him powerless so he can be given to the authorities. However, the female police officer taking him in turns out to be a disguised Charmcaster as she proceeds to enact a painful vengeance upon him. In "Charmed, I'm Sure", it is revealed that she turned him into a miniature rock figure. He saves himself from being crushed by whispering a "good reason" to Charmcaster. He is eventually freed-along with Adwaita, Hex, Gwen, and Bezel, who had all been similarly transformed-thanks to Gwen and Ben's teamwork.

A younger variation of Michael Morningstar appears in the 2016 reboot. This version is an actor who plays the lead role in the movie "The Unalivers", a Twilight parody. Not only does Michael maintain his ability to absorb life energy, but his powers can also be derived from the attention he gets from others.

The Incurseans

The Incurseans (Spanish word for "invasion") are a race of violent toad-like aliens with New York accents, forced to become spacefarers after the eon-long civil war on their homeworld ended a millennia ago when one Incursean stole Ascalon from Azmuth and destroyed the Incursion homeworld from misusing the weapon. Though making small appearances in earlier episodes, the Incursions become more of a threat during arc three of the Ben 10: Omniverse series until Milleous is removed from power with Attea taking over.

Sevenseven

Voiced by:

• Dee Bradley Baker - Ben 10: Alien Force, Ben 10: Ultimate Alien and Ben 10: Omniverse

Sevenseven is an alien bounty hunter who is from the same species as Sixsix, but far more dangerous. Much like Sixsix, he does not speak a word of English, even when talking to those who do, but other aliens have been shown to understand him. Unlike Sixsix, who uses weapons hidden in compartments of his armor, Sevenseven's hands can transform into various weapons and tools. It is mentioned that Sevenseven is Sixsix's older brother.

In "X = Ben + 2", Sevenseven had captured Princess Attea near Earth causing Emperor Milleous to target Earth for destruction. Princess Attea later paid him to help overthrow her father, but both of them were defeated by Ben.

Sevenseven returns in Ben 10: Ultimate Alien in "Hit 'Em Where They Live", he attempts to kill Ben's mom. Fortunately, Max stops him by making his jetpack overload so that it launches him into the sky. In Big Story he confront Gwen and Kevin in a factory but is defeat with easy by Rath.

Sevenseven returns in Ben 10: Omniverse, in Vilgax Must Croak in company of his brother Sixsix and sister Eighteight who are hired by Attea to murder Vilgax but his plans fail when Ben, Rook and Plumbers group's defeat them. He make a cameo in "OTTO Motives" in company of his sister Two Two in the auto-show Tetramand. Then in "Cough it up", he returns along with his siblings, Sixsix and Eighteight to help Psyphon with another evil plan.

Albedo

Voiced by:

• Yuri Lowenthal - Ben 10: Alien Force, Ben 10: Ultimate Alien, and Ben 10: Omniverse (in 16-year-old Ben form)
• Eric Bauza - Ben 10: Omniverse (in Galvan form)
• Tara Strong - Ben 10: Omniverse (in 11-year-old Ben form)

Albedo is a brilliant, albeit arrogant, rude and sociopathic Galvan. He was originally Azmuth's assistant, having first met Ben during the events of "Trouble Helix" where he played a role in Malware's evolution despite attempting to kill him. But later, taking Azmuth's refusal to make him an Omnitrix hard, Albedo built his own. However, though it functioned like Ben's, the Omnitrix that Albedo made was of inferior quality and turned him into a clone of Ben as the result of the two Omnitrixes being synchronized. As a result, Albedo also developed many of Ben's cravings and habits, which he considers utterly repulsive: Developing a craving for chili fries, even more than Ben himself, calling it a "human weakness" and denying having a liking for them.

Formally introducing himself as a clone of Ben in "Good Copy Bad Copy", Albedo tried to get Ben's Omnitrix, believing it would be able to turn him back to his original form. When Ben eventually met him during his rampage at a Forever Knight castle, Albedo pretended to be the creator of the Omnitrix, accusing Azmuth of being a liar, and asked Ben to give it back to him. When Ben realized that he was lying, he refused and Albedo attacked him in order to take his Omnitrix by force. After clashing with him twice, their Omnitrixes locked with each other, almost causing a feedback that could have destroyed a whole galaxy. During the process, Albedo's human form was damaged as he becomes white-haired and his clothes and eyes becoming red. Azmuth then arrived and removed the head plate of Albedo's Omnitrix, trapping him as a human while sent him to prison in the Null Void. In the series finale "The Final Battle", Albedo eventually escapes from the Null Void, teams up with Vilgax, stealing the Ultimatrix and completing it with pieces from his broken Omnitrix and tools given by Vilgax, yet could not return to his original form. Vilgax then offered him an alliance, promising he would let him get Ben's Omnitrix. Though not really trusting him, Albedo accepted and helped him. Despite the alliance being a success, Vilgax double-crossed Albedo and made him his prisoner. After the Omnitrix was destroyed, Ben freed Albedo and forced him to hand over the Ultimatrix by triggering the self-destruct command.

Marooned on Earth after Vilgax's ship exploded, Albedo has been running "show business" and playing the role Ben in his live action show, "Ben 10: Live", hiring three aliens to play Ben's top most popular aliens: Swampfire, Humungousaur, and Big Chill. Albedo intended to use the money to buy equipment in order to return to his Galvan form and leave Earth. However, not wanting the troupe to break up, the Vaxasaurian actor named Hugh lied to Ben's group that Albedo intended to build a Doomsday Bomb that will turn everyone on Earth into copies of Ben. But after Ben interfered, Albedo explains the device's purpose and how it both enabled him to shape-shift without an Omnitrix and gives no more reason to kill Ben. However, Ben's Ultimatrix caused the device to make Albedo's human form permanent, driving Albedo to attack Ben with his new powers before being knocked out and left in Hugh's care.

In "Night of the Living Nightmare", Albedo attempts to get even with Ben, by using a Dream Eater to trap him in a nightmare version of Bellwood, only to end up being the one subjected to the Dream Eater.

Having appeared in the flashback episode "Trouble Helix", Albedo makes his return in the Ben 10: Ominverse episode "The Ultimate Heist". With the assistance of Kyber, Albedo manages to trade places with Ben to develop a new Ultmatrix that would restore his Galvan form and evolve himself into an Ultimate Galvan state with the ability to assume the Ultimate forms of various aliens. From there, as seen in "A Fistful of Brains" and "For a Few Brains More", Albedo plotted to steal Azmuth's intelligence to augment his own. However, briefly caught in an enlightened state after absorbing the intelligence, Albedo is defeated. As an added punishment by Azmuth, Albedo ends up trapped in the form of Ben as an 11-year-old.

Albedo later returns in "And Then There Was None"/"And Then There Was Ben" two-part episode as part of the group of evil alternate Bens that Vilgax and Eon are recruiting across the multiverse. He joins Bad Ben, Mad Ben, and Benzarro in battling Gwen 10, Ben 23, and Ben 10,000 before all of them are temporarily erased from reality. However, this is later undone by the efforts of a Ben whose universe lacks an Omnitrix, only for Albedo and the other villains to be defeated. He later returns in "Malgax Attacks" having once again formed an alliance with Vilgax and uses the remains of Malware to create Mechamorph armor for Vilgax to use against Ben. He succeeds in vaporizing Azmuth only for his former mentor to be saved by Blukich and Driba. After his Ultimatrix is disabled, he is put to work cleaning up the damage from the attack.

Psyphon

Voiced by:

• Dee Bradley Baker - Ben 10: Alien Force, Ben 10: Ultimate Alien, and Ben 10: Omniverse

Psyphon (possibly a play on siphon, meaning drain or leach, due to his aid in draining the heroes of the conquered worlds) is Vilgax's servant and right-hand man. He is extremely loyal to Vilgax and follows his will completely; helping him to drain all the powers of the heroes of the 10 worlds he had conquered.

Psyphon returns in the Ben 10: Ultimate Alien episode "Reflected Glory", he seeks to avenge his master's defeat by destroying Ben's "puppet masters", Cash and JT, bringing with him three R.E.D.s (short for Robotic Extermination Devices). In that episode, he displayed the power to fly, create red energy beams and barriers, and had enough physical strength to pummel Ultimate Spidermonkey into submission. He was weakened when JT and Cash used a Power Decoupler to drain out his energies. He then appears in the 2-part episode "The Ultimate Enemy" where he helps Vilgax absorbs Diagon.

Psyphon appears in Ben 10: Omniverse, having become slightly buffed as he intended to become his own master by setting up a protection racket based in Undertown. However, in "The More Things Change" 2-parter, Psyphon was becoming interested in Rook's arsenal during their fight. Psyphon and his henchmen are defeated and arrested by the Plumbers. In "Outbreak", Psyphon ending up being accidentally turned into Pyronite. He was restored to his original form when Blukic and Driba get the Omnitrix fixed. In "Special Delivery", Psyphon auctions off a Dwarf Star that Corvo was to bring to him but accidentally grabbed one of Ben's delivery bags by mistake. When Ben gets his hands on the Dwarf Star, Psyphon attacked him with the aid of Fistina, Zombozo, Trumbipular, the Vreedle Brothers, Fistrick, Vulkanus, Sundar, and Seebik. When Ben defeats most of them, Psyphon absorbs the powers of the Dwarf Star. When Ben becomes Toepick, he reveals Toepick's face enough to scare Psyphon and claim the Dwarf Star.

Eventually, losing respect from even his own followers, Pysphon decides to come crawling back to Vilgax by the events of "Bengeance Is Mine". However, like everyone else at the time, Psyhon mistook a plumber named Bill Gacks for a disguised Vilgax and is the only one who believes it after Gacks helped in his capture.

Ssserpent

Voiced by:

• Dee Bradley Baker - Ben 10: Alien Force and Ben 10: Ultimate Alien

Ssserpent is a snake-like alien able to shed his skin, introducing himself as the "serpent that walks like man." He was first introduced in the "Vengeance of Vilgax" 2-parter, proving too tough for Gwen and Kevin before being easily defeated by the arrival of Cannonbolt. Since then, Ssserpent's appearances since have him suffering defeat by Ben's alien forms.

However, in "The Perfect Girlfriend", Ssserpent had learned from his mistakes and managed to set up an arrangement for Ben to use Goop so he can trap him to a giant centrifuge. Though Goop was saved by the police before the damage got too severe, Sserpent escaped.

The Vreedle Brothers

Voiced by:

• John DiMaggio - Octagon Vreedle - Ben 10: Alien Force, Ben 10: Ultimate Alien and Ben 10: Omniverse
• Rob Paulsen - Rhomboid Vreedle - Ben 10: Alien Force, Ben 10: Ultimate Alien and Ben 10: Omniverse

Octagon and Rhomboid Vreedle are a pair of "Repo men" who happen to be the sons of the infamous criminal Ma Vreedle, having very limited intelligence and theirs occupation includes bounty hunting and mercenaries for hire. Octagon is the older brother, slightly more intelligent with more mature, serious and down-to-earth personality, yet can still be easily tricked such as when Gwen distracted him and his brother with bubble wrap. Rhomboid is the least intelligent of the siblings who is the brawn of the two with a habit of always blowing things up with a large weapon. As he is the younger brother, despite being larger in size, he usually follows Octagon's orders with occasional foul-ups on his end. The Vreedle Brothers are physically weaker than most of Ben's enemies and appear to be no stronger than a normal human. However they make up for this with a large arsenal of various Alien weapons; and have a tendency to blow things up, which results in them having numerous run-ins with the law. The Vreedles are revealed to be multiple clone pairs created by their parents using an "expired cloning kit". Despite being basically defective clones, the Vreedles have a form of semi-immortality, meaning even if they are killed, usually by explosions they caused, their memories are transferred into another "set" of clones who will take their place.

They first appear in "Vreedle, Vreedle", hired by Baz-El to return Ship back for him. After Judge Domstol found the case in favor of Ben, Baz-El ordered the Vreedle Brothers to drop from their mission, but they denied that request causing them to be fended off by Ben and Kevin. In "Busy Box", attempting to steal it only to bring it back when it proved too much for them, the Vreedles were destroyed by the Naljian Destructor destroyed their ship in mid-flight. In appearances soon after, Ben's group encounters another pair of Vreedles with Rhomboid blabbing about their origins as clones.

Another "set" of Vreedle returns in Ben 10: Ultimate Alien episode "The Enemy of My Enemy", where their father enlisted them to the Plumbers' Academy, sending Argit to fix their grade upon learning they are failing in their exams. When Ultimate Kevin attacked, the Vreedles tried to help by using a nuclear bomb grenade against him, unaware that the device would kill everyone in the vicinity. After Kevin left, following his advice to pretend they do not know him to the letter, the Vreedles arrest Argit on Magister Korwak's orders.

The Vreedle Brothers appeared in the Mother of all Vreedles" where they were back to their old roots by their mother and helped her create clones of their younger brother Preety Boy Vreedle with Earth's oceans. After their mother tried to dispose of them, Vreedles resolve to arrest their mother with Ben's group promising not to reveal the brothers' moral relapse. Unfortunately as revealed in Ben 10: Omniverse, the Vreedles accidentally blew up the entire Plumber academy in a moment of weakness and have been on the run since. They make their return in "So Long, and Thanks for All the Smoothies?", getting their hands on the Annihilarg without thinking of the consequences of it until it was too late.

In "Special Delivery," the Vreedle Brothers are among those who help Psyphon to fight Ben and reclaim the Dwarf Star.

In "Oh, Mother Where Art Thou?," wanting to win their mother's respect, the Vreedles borrow one of the Pretty Boy clones to help them commit crimes. Though the scheme failed, they managed to win Ma Vreedle's respect due to abducting the Pretty Boy and stealing the core of a missile their mother was going to use on the sun.

They also appear in Cartoon Network: Punch Time Explosion as an assist characters with a synergy attack with Mojo Jojo.

Sunder

Voiced by:

• Powers Boothe - Ben 10: Alien Force and Ben 10: Ultimate Alien
• David Kaye - Ben 10: Omniverse

Sunder the Retriever is an alien bounty hunter. He has an axe which is able slice through things. It can also send whatever it slices to a different dimension, as he was able to send Ben (minus his Omnitrix hand) to the Null Void. He also uses a Hover Board for transportation; inside he has many gadgets, to use or to sell.

He was sent by Vilgax to pursue Ben and to try to remove the Omnitrix using his energy axe to bring to his master, sending Ben to the Null Void, but left only Ben's left hand on Earth. When the hand is found by Julie, she brings it to Gwen and Kevin. Kevin invented a machine to bring Ben back; it was a success except that Ben's left hand is now in the Null Void. As Sunder charges toward the group, Kevin activates the machine again and restores Ben's left hand to his body but sending Sunder to the Null Void. Sunder was then seen trying to reclaim his axe from one of the alien creatures there.

Sunder returns in the Ben 10: Ultimate Alien episode "The Transmogrification of Eunice", where he was released from Null Void and sent by Azmuth to retrieve the Unitrix (which turned into Eunice). Ben convinces Azmuth to let Eunice have a normal life and be one of his assistants as he always needs a helping hand tending Primus, as it needs some help and care. Before teleporting away with Azmuth and Eunice, Sunder asks Azmuth if he is still getting paid for his services.

In Omniverse, Sunder resumed his attempt to take the Omnitrix as seen in "Have I Got a Deal for You". This time, he is now shown wearing a helmet. He attacks Ben in Undertown and is sent flying by Shocksquatch. Sunder apparently didn't learn his lesson from the last couple times he came after an Omnitrix.

He reappears in "Special Delivery" where he assists Psyphon in claiming the Dwarf Star. Ben was able to defeat him easily. In "Cough it Up," He is recruited by Psyphon to carry out another evil plan, but is defeated by Ben, Rook and Spanner.

Jarret

Voiced by:

• Alexander Polinsky - Ben 10: Alien Force and Ben 10: Omniverse

Jarrett is a Panthopage and the King of its kind, first appears in Ben 10: Alien Force in the episode "Con of Rath", where required to the Queen of Sicily and Zaw Weenel Ambassador to bring to Tiffin to his planet with the intention of devouring him as a way of avoiding conflict. Rath literally jumped down Jarrett's throat to recover the Tiffin, threatening to do so again, but with a more gruesome result.

In "Color of Monkey", Jarret hires Argit to capture a Tiffin. When he received the delivery, Jarett was dismayed to find artificial Tiffin in the delivery box instead (courtesy of Ben's interference). He grew angry and attacked Argit and his Techadons.

Diagon

Voiced by:

• John DiMaggio - Ben 10: Ultimate Alien

Diagon (named after Dagon) is an thousand years old energy-based cephalopod-like inter-dimensional being, very similar to Cthulthu.

He was claimed to visit Earth during the Middle Ages, and gave humans advanced technology. He is believed to have sworn to come back to Earth to bring the "Golden Age", claiming he will bring more alien technology and make Earth a Utopia. But actually, he tried to invade this dimension in a "dragon" form with the help of his Lucubra army. He was banished back to his dimension when Sir George defeated him by cutting out his heart with the sword Ascalon that was given by Azmuth.

He was first mentioned in "Flame Keepers' Circle" where Vilgax was mistaken by the Flame Keepers' Circle and they thought he was Diagon. In "The Ultimate Enemy", while he attempted to break the seal, Diagon converts most of Earth's people into Esoterica to be his followers before taking control of Gwen's mind to have her finish the task. Though that attempt failed, Diagon manages to enter reality by destroying the seal from his side. After defeating Ben and killing Sir George, he meets his apparent end when Vilgax has him be sucked into an energy absorbing device. Vilgax received all of Diagon's power, but Ben used Ascalon to defeat Vilgax by absorbing Diagon into it and revert all of the Esoterica back to human.

Will Harangue

Voiced by:

• John DiMaggio - Ben 10: Ultimate Alien and Ben 10: Omniverse

Will Harangue is a loud-vocaled television newscaster who hosts "The Harangue Nation" on cable. Since Ben's action became public knowledge, possibly to garner ratings, Harangue launched a smear campaign against Ben and constantly tries to denounce him as a threat to humanity. However, though still getting on Ben's nerves whenever he watches Harague's show, only a few actually bought into his propaganda.

Harangue had gotten his hands dirty starting in "Video Games", where he has Oliver Thompson aid him in tricking Ben into showing all his aliens' moves to give his giant robot "the Stalker" an advantage. But after the Stalker is eventually dismantled by Ben as Nanomech before becoming Way Big to crush the robot while "accidentally" dropping it on his car, Harangue covered his tracks by firing Thompson and altering the footage to portray Ben in a negative light.

In "Hero Time", Will Harangue worked with Captain Nemesis in a plot to have Captain Nemesis outdo Ben. He even arranged a contest between Ben Tennyson and Captain Nemesis with Jennifer Nocturne as his field correspondent. After Ben as Four Arms beat Captain Nemesis in the final event revolving around tug-of-war, Will Harangue commented that he can't say Ben cheated, but will let the viewer decide. After Captain Nemesis was arrested following his defeat at the hands of Ben, Will Harangue commented on this stating that a good man did terrible things all in the pursuit to stop the "menace that is Ben Tennyson."

In "The Big Story," Jimmy Jones appears on Will Harangue's TV show where Will reports that Ben (actually a plant clone of Ben) is working for a giant Plant Monster. Although he acknowledges Jimmy for providing photos of Ben as aliens, Will does not seem to take him seriously. In "The Mother of All Vreedles," Will Harangue reports on a meteor.

Returning in the 2-part Omniverse series episode "The Frogs of War", Harangue launched a smear campaign on Ben for the escaping aliens from Undertown. But once the Incursions conquered Earth, Harangue sided with the current occupation to broadcast propaganda-based news as he claimed that the World Leaders had "exiled" Ben and had welcomed the Incursions as their saviors. That action led to his show suffering lowered ratings with less sponsors, forcing him to fund Chadwick during the events of "Return to Forever" while ignorant of the Forever Knights' actual intentions. Ben as Juryrigg rewired the machine to turn Harangue into a mutant squid-like alien.

In "The Vengers," Will's present self also appeared and he reported about the Vengers' exploits, making his ratings even higher. In reality, however, they also doubled as a citywide smear campaign against Ben in order to boost the credibility of the Vengers, with himself being an unofficial secret partner. After the people realized that the Vengers became what they had always been (which is supervillains), he betrayed them immediately keeping his ratings as high as they were before. All while still trying to smear both Ben and Billy's team to cover up the fact that Billy had Harangue edit footage of the Vengers battle with Tennyson to discredit the latter further, all in a semi-vain effort to save face.

Aggregor

Voiced by:

• John DiMaggio - Ben 10: Ultimate Alien

Aggregor (a play on "Aggregate") is an artificial Osmosian who became an intergalactic criminal, later revealed as an enhanced clone that Servantis created from Kevin's DNA to destroy Ben after the Amalgams failed. But Ben swearing off the Omnitrix resulted with Servantis letting Aggregor loose into the universe after wiping out his memory. Like Kevin, Aggregor can absorb any type of matter and energy and use them by force of will, with his own natural abilities, or with his staff. While he uses robots, Aggregor prefers to carry out his plans himself rather than let his henchmen do the work. Aggregor is a highly skilled hand-to-hand combatant and carries a powerful spear which he can use as either staff or spear to stab targets or fire blasts of red energy that can disrupt other energy fields, stun targets or disrupt machinery.

Aggregor plotted to kidnap five aliens of different species from the Andromeda Galaxy so he could drain them of their powers with a machine he built back on his home world. Using their combined powers, he would become strong enough to search for and reassemble the four fragments of the Map of Infinity so he could travel to the Forge of Creation to absorb the powers of a newly born Celestialsapien and become omnipotent. Aggregor managed to absorb the aliens' powers and obtain the four pieces of the Map of Infinity. But Kevin absorbed DNA samples from Ultimatrix to siphon the alien DNA out of Aggregor, reverting the Osmosian back to his original form before being eventually handed over to the Plumbers.

Aggregor was originally supposed to appear in Ben 10: Omniverse during the "Rooters" arc, but this planned appearance was scrapped.

Carl Nesmith

Voiced by:

• Christopher McDonald – Ben 10: Ultimate Alien and Ben 10: Omniverse

Carl Nesmith was a famous superhero known as Captain Nemesis, a great American icon, and Ben's idol. He stated that he'd been a hero before Ben was even born, and his long services made him rich and famous, having his own weapon-making company and comic book series. But in reality, he is a greedy gloryhound and a fraud who recently stages all criminal activities he seemingly stopped to get fame and fortune.

He was first introduced in "Hero Time", where his faked kidnapping ploy with famous actress Jennifer Nocturne to get him back on the news was foiled by Ben, which developed an insane jealousy rivalry with Ben. After a second attempt to get back credit was again unwillingly spoiled by Ben, Captain Nemesis proposed a "friendly competition" between the two of them to see who the best was. Though he was able to win one test thanks to an Ultimatrix malfunction, he ended up being humiliated by Ben, ruining his image. After his defeat, Carl was jealous and rancorous toward Ben, and upgraded his armor in a dangerous way to get revenge on him. He then kidnapped Julie and intercepted Jennifer Nocturne's helicopter in order to bring Ben to him for a rematch. Captain Nemesis endangered Julie and Jennifer's lives to force Ben through a "no-win" situation game. Ben saved Julie, while Gwen and Kevin saved Jennifer. During this time, Carl expressed a disgust and disillusionment for having "wasted" his life saving pathetic people like Ben, so he renamed himself Overlord, stating that Captain Nemesis is retired. After defeated, he is then arrested by the police. Will Harangue reported on this and commented that a good man did terrible things all in the pursuit to stop "the menace that is Ben Tennyson."

Carl Nesmith returns in "Catch a Falling Star" where he breaks out of prison with help from Jennifer Nocturne (who had developed Stockholm syndrome feelings for him due to her personal life crisis). Though getting plastic surgery to look younger so not to be recognized by the police, Nesmith was still bent on getting revenge on Ben. However, having feelings for Jennifer, Carl returns to jail when she is injured and covers up her role in his escape.

He returns later in Ben 10: Omniverse. In "The Vengers" is released from prison along with Kane North by Billy Billons to form team the Vengers and become future heroes of Bellwood, but in the end are considered villains and they are defeated by Ben and Rook.

Computron

Voiced by:

• Dee Bradley Baker - Ben 10: Ultimate Alien

Computron was imprisoned in Dimension 12 but it was later freed by Captain Nemesis so it could save people from it and its robot minions, but Ben arrived and destroyed all of the robots using Jetray and Armodrillo. However, Computron was destroyed by Captain Nemesis by taking his fist and popping his head off.

King Xarion

Voiced by:

• Peter Stormare - Ben 10: Ultimate Alien

King Xarion was the aging King of the kingdom of Zarcovia. He appears in "Viktor: The Spoils" asking the help of Ben and his team to stop his son Prince Gyula who tried to liberate Dr. Viktor. King Xarion is later imprisoned along with Ben and his team until he was released by Gwen. King Xarion then makes off with Ben and takes it along with Dr. Viktor to Gyula's laboratory to be transported to one of their bodies. In doing where Ben Tennyson stops this, it led King Xarion's mind being in the body of Viktor and using it to eliminate its enemies. King Xarion in Viktor's body was stopped by Ben and his team to catch it on hardened metal.

He reappears later in Omniverse in "Rad Monster Party" in the flashback of Zs'Skayr when his conscious was finally destroyed by the Ectolord allowing Dr. Viktor to officially come back to life.

Pa Vreedle

Voiced by:

• Jeff Bennett - Ben 10: Ultimate Alien
• Steven Blum - Ben 10: Omniverse

Pa Vreedle is a Vreedle who is the father of Octagon and Rhomboid Vreedle. He first appears in "The Enemy of my Enemy" forcing Argit to infiltrate the Academy of Plumbers that Octagon and Rhomboid to pass their exams. Pa Vreedle returns later in "Vreedlemania", where he forms an alliance with Ma Vreedle so that they along with all of his children run destruction in the town of Bellwood.

According to Derrick J. Wyatt, Ma Vreedle and Pa Vreedle were made in a lab by extremely substandard scientists.

Trumbipulor

Voiced by:

• Dee Bradley Baker - Ben 10: Ultimate Alien
• Eric Bauza - Ben 10: Omniverse

Trumbipulor is an elephant-like alien.

He first appears in the episode "Basic Training" where he was seen committing illegal trading of Level 3 technology until he was defeated by Ben, Gwen, and Kevin and arrested by the Plumbers.

In "The Purge", Ben, Gwen, and Kevin fought Trumbipulor again. Ben fought him as NRG, but Trumbipulor escapes

In the Omniverse episode "Blukic & Driba Go to Mr. Smoothy's", Trumbipulor was redesigned with smaller ears and his mouth is now at the end of his trunk. Trumbipulor fought Ben and Rook in order to find the "absolute power" which turned out to be peanuts. When Trumbipulor's kind eats peanuts, they grow to large size. As Echo Echo, Ben took advantage of Trumbipulor's super-hearing and blasted him with sound waves.

In "Special Delivery", Trumbipulor is seen at Psyphon's auction. He is among those who help Psyphon fight Ben and reclaim the Dwarf Star that was to be auctioned off.

Inspector 13

Voiced by:

• Dee Bradley Baker - Ben 10: Ultimate Alien and Ben 10: Omniverse

The Weapons Masters of Techadon create, supply and sell weapons to anyone who can afford them from their homeworld of Techadon. They are incredibly anti-social and usually never leave their home planet, as stated that no one has ever seen one of them; but actually, no one has ever seen one of them and survived. They are cold and calculating with no concern only the intent of those who buy their products, only caring to make better weapons than the Galvans. To that end, there are times when the Weapon Masters steal technology from other advanced alien races and fit them for combat purposes.

Due to the events from both "The Gauntlet" and "Greetings from Techadon" where their Technodon robots were sent to that planet and defeated, a Weapon Master known only as "Inspector 13" arrived on Earth to obtain the Ultimatrix and weaponize it. However, his humiliating defeat forces him to leave Earth and keep his attempt a secret from fellow Weapon Masters.

But by the events of Ben 10: Omniverse, making a cameo in "Special Delivery" before his official reappearance in "The Ultimate Heist", Inspector 13's failure became public knowledge and he ended up in exile as a free agent in arms dealing.

In "Clyde Five", Inspector 13 provides Liam a prototype exo-suit weapon that Clyde named the Cincotrix.

Malware

Voiced by:

• Corey Burton - Ben 10: Omniverse

Malware (named by Azmuth to reflect his nature to corrode anything he touched) is a red Galvanic Mechamorph, set apart from others of his kind by absorbing technology to "evolve" himself instead of the opposite effect. Malware was originally a yellow Galvanic Mechomorph whose life code was corrupted upon creation on Galvan B, possessing a razor-sharp physique and menacing claws in addition to his enhanced strength and natural abilities. As revealed in "Trouble Helix," suffering physical pain, Malware was waiting for an upgrade for his condition and sought out Azmuth and learned of the secondary Helix he created. Taking the Helix to Galvan B to fit it into the first Helix, Malware assumed a red-armored form with his assimilative ability and made it his goal to obtain the Omnitrix to further evolve himself.

Though defeated by the eleven-year-old Ben on Galvan B, Malware followed the boy to Earth and fought him as seen in "The More Things Change" Pt. 1. As revealed in "Of Predators and Prey" 2-parter, Malware managed to scan a copy of the original Omnitrix design for Dr. Psychobos to create the Nemetrix. Prior to the Nemetrix's completion, Malware's body structure altered into a monstrous-form after being inflicted with a blast that altered his being at a sub molecular level and later was seemingly destroyed after being overloaded while absorbing the Omnitrix.

In "Of Predators and Prey" Pt. 2, Malware and Dr. Psychobos arrive and confront Khyber and his Dog after their ship had crashed outside of Bellwood. Malware later reintroduced himself to Ben during the events of "Malefactor" while taking Galvan security codes from the Plumbers' mainframe, using a tanker truck as a diversion to get away. Malware later makes his move during the events of "Showdown", having Dr. Psychobos and Khyber provide a distraction to enact his scheme to wipe out the Galvans by destroying Galvan B with his remains seeping in Galvan Mark II to assimilate the planet. Upon regaining his ability to become Feedback, Ben places Malware in a petrified state. However, Malware's body was retrieved during "Malgax Attacks" and transfigured into a suit of armor that Vilgax uses. The suit was later calcified after it and Vilgax were thrown into the warp core of Vilgax's ship, but some of Malware's substance was seen emerging from a crack in it as it floated in space.

Khyber

Voiced by:

• David Kaye - Ben 10: Omniverse

Khyber the Huntsman is a hunter who was hired by Malware and Dr. Psychobos to go after Ben, told he was a worth prize to hunt. To aid in his hunt, Khyber is given an Omnitrix-like item called the Nemetrix which he uses to turn his pet Anubian Baskurr hunting dog-like alien Zed into any predatory species to counter any of Ben's alien forms. In his spaceship, he keeps his collection of trophies from previous hunts including an Appoplexian skeleton, a Vaxxasaurian skull, and a Geochelone Aerio shell. At first, Khyber stayed in the shadows, infiltrating Max's Plumber base during the events "Trouble Helix" to obtain a history file of Ben's fight with Malware. Kyber eventually made himself known to Ben in "Of Predators and Prey" the 2-parter, capturing Ben and revealing the origins of the Nemetrix prior to being defeated as his ship crashes.

Surviving with the intent to make Ben pay, Khyber moves into Malware's ship and since helped in Malware's schemes until the events of "Showdown" where he aided Psychobos before they two enter into an argument of interest. After Azmuth managed to use a whistle to control Zed to defeat Psychobos, Khyber managed to swipe the Nemetrix off his dog while nobody was looking and escapes, and the Galvans took her collar off of her and became Kevin's pet, after obtaining a Panuncian as his new hunting animal, Khyber teams up with Albedo by aiding him in his escape during the events of "The Ultimate Heist" to enact a plan to capture Azmuth.

As a benefit, Khyber gains a new model of the Nemetrix that enables his new pet, a Panuncian, to access its ultimate form. When Albedo is defeated, Khyber escapes again and resurfaces in "Stuck on You" where he employs Skurd to personally utilize the Nemetrix without its side effects on sapien life forms. However, Skurd's transfer to Ben resulted with Khyber, suffering minimal side effects, finally arrested.

Panuncian

A rare animal Khyber uses in place of Zed since she now belongs to Kevin, a Panuncian is a saber-toothed cat-like alien that is the natural predator of a Splixson (Ditto's kind) as its ability to split makes it a one-beast pack. Having been fitted with the Nemetrix, the Panuncian 's splitting ability is utilized by Khyber to have access to all Nemetrix alien forms at once. Using its Nemetrix's Ultimate Alien function, the Panuncian can increase its size and is outfitted with armor on its head and spikes across its body.

Dr. Psychobos

Voiced by:

• Eric Bauza - Ben 10: Omniverse

Dr. Psychobos is a mad scientist Cerebrocrustacean who frequently uses "and I use the term loosely" when mentioning others and has an intent to prove the intellectual superiority of himself and the Cerebrocrustaceans over Azmuth and the Galvan race. The latter aspect of his personality playing a role in allying himself with Malware's business partner and creating the Nemetrix. Dr. Psychobos formally introduces himself to Ben during the events of "Outbreak" when he stole part of Ben's Omnitrix to repair the Nemetrix. He later enacts his plan to kill Azmuth during "Showdown" with Khyber before being abandoned by the hunter and then placed under arrest.

In "While You Were Away", Dr. Psychobos was sprung from prison by Princess Attea and forced in her services at the time when the Incursians invaded Revonnah. With the mind control serum he developed, Dr. Psychobos also provided the Incursians with the Way Bads during their occupancy of Earth as seen in the two-part episode "The Frogs of War." In the end, Dr. Psychobos's control over the Way Bads is negated as the Way Bads are sent into the Null Void by Rook, Blukic, and Driba. Being arrested soon after, Psychobos resurfaced in the "It's a Mad, Mad, Mad Ben World" two-part episode to repair Maltruant. But Psychobos ends up being betrayed and left behind in Mad Ben's universe, later formulating a scheme to kill off Ben and Ben 23 but ending up being jailed alongside Mad Ben.

Undertown Thugs

A group of criminal aliens that reside in Undertown, most of time hired by Psyphon in different plans but act on their own whims in other criminal acts.

Fistrick

Voiced by:

• Eric Bauza - Ben 10: Omniverse

Fistrick is a super-strong small-time crime lord and arms dealer. He has a lot of connections, often responding that he "knows/knew a guy" as the answer to question. Ben and Rook first encounter Fistrick when he and his henchmen were abducting Megawhatts and using them to power up the technology that he has reverse-engineered. In the fight between Ben and Rook, Fistrick uses a powerful exo-suit that is powered by Megawhatts. As Gravattack, Ben was able to defeat Fistrick and hand him over to the Plumbers while the Megawhatts were relocated to Undertown.

In "Bros in Space", Fistrick acquired a planet-destroying satellite and positioned it near the planet Revonnah so that he could use the planet's Amber Ogia as fuel for the weapon. Upon heading to Revonnah, Fistrick trained the local Muroids to steal the Amber Ogia for him and pilot his Mecha-Harvesters. Ben and Rook discovered the plot while visiting Rook's family on Revonnah. Fistrick brought Ben to his planet-destroying satellite intending to kill him with it, but Ben narrowly escaped the death trap. As Kickin Hawk, Ben defeated Fistrick and the Muroids while Rook rallied his people and defeated the Muroids.

In "Special Delivery", Fistrick is seen at an auction held by Psyphon. He later helps Psyphon attack Ben and reclaim the Dwarf Star.

He returns in "No Honor Among Bros", where he escapes from the Plumber HQ using a concoction based on his own sweat with Fistina in order to participate at the Golden Fist Tournament. As an unintended side effect his concoction poisons Rook's brain with his essence, leading Rook to act like Fistrick. He defeats Bahrvad by throwing salt into his face and outwits Fistina using a mechanical disassembling device but is defeated by Rook Blonko.

In "Universe Vs. Tennyson", Fistrick hijacked Mr. Baumann's truck and forced him to drive around. Fistrick soon found himself fighting Ditto but started to gain the upper hand after Ditto transformed back into Ben. However, when Fistrick tackled down Ben, he landed on the gas pedal which made the truck smash into a wall. Fistrick was then arrested by Ben and Rook and was taken to Plumber's HQ. Ben wondered how Fistrick got out of jail so fast and it turns out to be by Chadzmuth. Chadzmuth then forced the Plumbers to release Fistrick and Fistrick was pleased by this. At the end of the episode, Fistrick was arrested again but it can be assumed that Chadzmuth freed him and the other villains once more.

He is the main villain in "Breakpoint" as he and his fellow criminals disguise themselves as different versions of Ben to commit hijackings of alien tech shipments. However, Fistrick and his gang are eventually apprehended, with Fistrick being beaten by Molestache. He is then given the ultimate insult by Ben in his jail cell by being fed a meatball sub and chili fries.

Solid Plugg

Voiced by:

• Eric Bauza - Ben 10: Omniverse

Solid Plugg is a thug for hire appearing in Ben 10: Omniverse, having a criminal record. Though short, Solid Plugg is very strong. He first appears in the 2-part episode "The More Things Change", shopping his groceries at Mr. Baumann's shop before making his official introduction in "Have I Got a Deal for You" where he was an assistant of Professor Blarney T. Hokestar.

Princess Looma Red Wind

Voiced by:

• Kimberly Brooks - Ben 10: Omniverse

Princess Looma Red Wind is a female Tetramand who is a princess of Khoros and Gar`s daughter. Long ago she met Kevin when Argit and he went to their planet to seek an advanced engine but to get it he had to accept to marry her. After agreeing to do so Kevin leaves her taking the engine with him, this led her to seek out Kevin and complete the wedding. She appears in "Many Happy Returns" after a long search to find Kevin, she arrives on Earth. Kevin tries to hide with Ben, but is eventually found by Looma. Rook and Gwen try to stop her until Ben fights and defeats her as Four Arms. Her father says that Ben is now engaged to her and she promises to return three years later.

She returns in "Rules of Engagement" to search for wedding gifts. She kidnaps Esther, Julie, Rook, and Hervé for the wedding event. She is defeated by Ben as Ball Weevil and she left saying the engagement is now off and that Julie can have Ben. Despite this, she comes after Ben again in "Catfight" and winds up in a three-way fight over him involving Princess Attea of the Incurseans and Nyancy Chan. However, Ben eventually convinces both her and Attea that they are powerful rulers who don't need men by their sides, and they return home while Chan goes to prison.

Looma re-appears as a contestant in "The Most Dangerous Game Show", where her rivalry with Attea is temporarily rekindled.

Billy Billons

Voiced by:

• Aziz Ansari - Ben 10: Omniverse
• Gunnar Sizemore - Ben 10 (Reboot)

Billy Billions is a rich kid who was a rival of an eleven-year-old Ben Tennyson, due to jealousy of Ben's popularity. In a failed attempt to get rid of Ben, Billons ends up in the 12th Dimension and spends five years there without aging while building a device to control the robot residents of the dimension. In "Arrested Development", Billions makes his return and uses his army of Dimension 12 robots to enact revenge on Ben by turning him and Rook into eleven-year-olds. But when Billions loses control of his robots, he makes brief alliance with Ben and Rook to close the portal to the 12th Dimension in order to prevent the 12th Dimension robots from invade, before being arrested by the Plumbers.

Later in "The Vengers", Billy returns and bails out Kane North and Carl Nesmith from prison to form the team known as The Vengers to become the heroes of Bellwood, thus overthrowing Ben Tennyson's position, but in the end they return to their villainous habits and are defeated by Ben and Rook.

Billy returns in the reboot, relatively unchanged save for that motives for attacking are more focused on getting his own way. He also controls an assortment of robots through his tablet. The reboot also introduces his parents, who seem to be similarly villainous and expect their son to follow in their footsteps.

Nyancy Chan

Voiced by:

• Gwendoline Yeo - Ben 10: Omniverse

Nyancy Chan is a female criminal who is very obsessed with felines and a passion of cats which is similar to Catwoman from DC's Batman, and with an ability to control feline species and hypnotizing cats or anything cat-like to do her bidding.

She first appears in "Special Delivery" in the background at Psyphon's auction.

In "Tummy Trouble", Nyancy Chan fights with Ben and Rook where she is unable to control Rook and ends up defeated. Nyancy Chan is then arrested by the Plumbers.

In "Catfight", she returns and manipulates Ben while he is in the form of Rath to carry out her evil plans, but is defeated by Rook, Ester and Rayona.

EightEight

Voiced by:

• Dee Bradley Baker - Ben 10: Omniverse

EightEight is a bounty hunter and mercenary from the Sotoragg system. She is the sister of Sixsix and Sevenseven. Eighteight first appeared in "Vilgax Must Croak" where she and her brothers were hired by Princess Attea to kill Vilgax. She appears similar to her brothers but is more feminine and her armor is coloured pink with four red robotic lines for eyes.

Way Bads

Voiced by:

• Eric Bauza - Ben 10: Omniverse

The Way Bads are mutant Tokustars mutated by Dr. Psychobos to serve as Incurseans' mindless shocktroops during the events of the two-part "The Frogs of War" before they are transported to the Null Void by Rook after breaking Psychobos's hold over them. The WayBads later return in part 2 of "Weapon XI", first attacking Ben, Gwen, Rook and Argit during their escape from the Amalgamate kids and later after the Rooters were decommissioned and left behind in the Null Void.

Crujo

Voiced by:

• Bumper Robinson - Ben 10: Omniverse

Crujo is a brown Loboan working for Zs'Skayr. He first appears in "Rad Monster Party" alongside Kuphulu to carry out the release of Viktor and is then seen fighting Ben, Rook, Rad, and Hooble. "In Charmed, I'm Sure", Crujo and Viktor help Zs'Skayr in the task of draining the energy of the Alpha Rune.

Kuphulu

Voiced by:

• Jeffrey Combs - Ben 10: Omniverse

Kuphulu is a Thep Khufan who works for Zs'Skayr. According to Scout, Kuphulu is a small-time repeat offender.

Lord Transyl

Voiced by:

• David Kaye - Ben 10: Omniverse

Lord Transyl is the last of the Vladats, having reigned over Anur Transyl before his death. However, having obtained his hand, Zs'Skayr uses the energies of the Alpha Rune to resurrect Lord Transyl to convince him to join forces to take over Anur Transyl's population while resurrecting the Vladats race to extend their control to the rest of the universe, during the events of "The Vampire Strikes Back". When Zs'Skayr orders Lord Transyl to get Ben Tennyson under his control, Viktor turns against Lord Transyl and the plan fails, followed by Ben using Atomix to defeat Zs'Skayr and Lord Transyl. Afterwards, Lord Transyl is imprisoned by Viktor in a casket stationed to face the sun to keep him in a weakened state.

Rooters

The Rooters are a special Plumber black ops unit in the Null Void, holding higher rank than any Plumber branch and answer only to the High Protectorate. The Rooters saw Ben as a threat to the universe, motivating them into using Kevin Levin's powers to convert themselves and future members of the Plumbers Kids into alien hybrids to kill the boy. But the assassination plan failed and Servantis purged Kevin, Argit, and the Plumber Kids of any memories of the Rooters as the organization lets Ben be after his removed the Omnitrix. But when the Highbreed invasion forces Ben wears the Omnitrix once more, the Rooters decide to use Kevin and the Plumber Kids as sleeper agents to get close to Ben. The Rooters debut in "The Rooters of All Evil", having recruited Phil to their ranks while attempting to capture Kevin to begin their plan. But Kevin escape with the Plumbers' help before he eventually agrees to help Servantis during the events of "Weapon XI" two-parter where the Rooters regain their hit squad and sic them on Ben, Gwen, Rook, and Argit. But Kevin feigned loyalty to the Rooters' cause so he can frees the Plumber Kids from Servantis's control. The Rooters were then disbanded by the High Protectorate and left stranded in the Null Void at the mercy of the Way Bads.

Kundo

Voiced by:

• Jeff Bennett - Ben 10: Omniverse

Kundo is a Revonnahgander traditionalist who believes his people are being poisoned by the outside world, being the only member of his race to still hold that belief. While he was originally tolerable to allow Rook to join the Plumbers, Kundo was against Rook Sharr's enlistment and pursued her to Earth during the events of "Rook Tales" to bring her back to Revonnah by any means. But it resulted with Kundo being seemingly killed when subjected to the acidic Blastonium, later revealed to have survived the near-death experience with severe burns and cybernetic prosthetics. Driven further insane by his new nature as a cyborg, believing his actions are for the good of the universe, Kundo returned in "Final Countdown" to wipe out the Plumber bases with Earth's branch his first target. But Kundo is defeated and arrested after his plan is thwarted.

Maltruant

Voiced by:

• Mark Hamill - Ben 10: Omniverse

Maltruant (a play on "Mal" and "Truant") is a Chronosapian who seeks to control the time-space continuum, mentioned to have been involved in a time war before his body was broken in several pieces and placed in various points in time and space. Maltruant also played a role in Vilgax's obsession for the Omnitrix and visited the dimension of Mad Ben where he became the youth's second mentor figure. Maltruant first appeared in the episode "Fight in the Museum" when he hires Subdora and Exo-Skull steal the Key to Time, one of his many body parts, for him. In the first half of the "It's a Mad, Mad, Mad Ben World" two-part episode, Maltruant recruits Dr. Psychobos to complete the restoration of his body before going to the dimension of Mad Ben to gain the final piece of his body. Once completely repaired, allowing the latter to do whatever he likes to the former alongside Ben and Ben 23, Malruant leaves both Psychobos and Mad Ben behind while he proceeds to start a new time war with Eon providing him with two Time Beast eggs. In the two-part series finale, Maltruant then travels to Ben's future timeline to steal the Anihilaarg and modify it with a Dwarf Star before using the Time Beasts to reach the time before the universe began so he recreate it in his own image. But it resulted in Maltruant's destruction and, unaware of the significance, the beginning of an endless time loop where the Chronosapian would eventually be rebuilt and repeat his actions up to being destroyed again and again.

Hydromanders

Voiced by:

• Fred Tatasciore - Ben 10 (Reboot)

Hydromanders are tadpole-like creatures that first appeared on the episode "Waterfilter" They have dark green skin with whitish yellow belly, orange eyes and sharp teeth, orange dorsal fin on their heads, three tentacles on each side of the head, and a tadpole-like tail. Their behavior are extremely hostile, especially when someone disturbs them. After waking up, they eat everything around them and use their tongue to eat like actual salamanders. When they die, many smaller Hydromanders sprout from the corpse of the one that died. Apparently, the newborn Hydromanders have the memories of the one they came from. They can breathe and swim underwater, giving them enhanced speed and agility, stretch their tongue to a long distance which can grab anything and introduce it inside their mouth and if they are injured, it can regenerate quickly inside the mouth, and move the tentacles from their head and their tail.

Iron Kyle

Voiced by:

• Roger Craig Smith - Ben 10 (Reboot)

Iron Kyle is a wrestler from Midwest Wrestling that first appeared on the episode "The Ring Leader" and wears a robotic armor suit to fight in wrestling. With this, he has enhanced resistance and strength. His personality includes being quite arrogant and doesn't care about anyone else's well-being, hurts every wrestler he fights and even goes as far as to jump on the crowd in order to beat a harmless Crushster. Just like every wrestler, Iron Kyle doesn't show any shame for cheating, but he got depressed when his secret was revealed and he was expelled from Midwest Wrestling. He is quite smart as to create his own equipment.

Though he is stronger than Four Arms, he is almost beaten. However, the Omnitrix timed out and, angered, Iron Kyle attempted to crush Ben. When Ben finds out that water is his weakness, he turns into Overflow and sprays him with enough water to disassemble his armor. He and Overflow are ultimately kicked out of the wrestling building and eventually have a video game match.

Steam Smythe

Voiced by:

• Roger Craig Smith - Ben 10 (Reboot)

Steam Smythe wears grey and gold colored boots and has a brown pants, grey suit on with gold on it, brown and gold hat with a blue orb in the middle, steampunk technology all over his clothes, red mustache, beard, and hair, and brown eyes that first appeared on the episode "The Clocktopus." His partner (and mascot) Aristocraw, who helps Smythe with his machines. He is shown to be chauvinistic and old fashioned, considering himself a gentleman. However, he is highly intolerant of modern technology, believing that the past is the proper way for the future. He is demonstrated to be extremely intelligent, having made several steampunk based technology, including robots called Mechanoids and the Clocktopus, and is shown to have numerous devices in his suit, including a miniature cannon. It is also revealed that, although Smythe is older than Grandpa Max, he has seemingly retained a youthful appearance. Later in the series, Smythe's partner, Aristocraw abandons him and joins Team Tennyson after Steam Smythe calls him "useless".

Lagrange

Voiced by:

• David Sobolov (in "Drive You Crazy"), David Kaye (in "Need for Speed") - Ben 10 (Reboot)

Lagrange is an illegal racer with a heavy French accent that debuted on the episode "Drive You Crazy", seen driving a red race call.

The Malachi Sisters

• Voiced by:
• Tara Strong and Kari Wahlgren - Ben 10 (Reboot)

The Malachi Sisters are a pair of siblings who are illegal racers.

Lord Decibel

Voiced by:

• David Kaye - Ben 10 (Reboot)

Lord Decibel first appeared in the episode, "Don't Let the Bass Drop". He is capable of controlling sounds and amplify them to a degree to cause Earthquakes. His appearance is similar to Eon, wearing a helmet that purple coloured emoticons instead of his face.

Nanny Nightmare

Voiced by:

• Anna Vocino - Ben 10 (Reboot)

Nanny Nightmare has a grudge upon people and their maturity and wants to reduce everyone on Earth back to infantry. Luckily Ben (as Upgrade) and Gwen are able to stop her by reversing the polarity of her machine, aging her and her henchmen. She has purple hair shaped into devil horns and wears 1930's attire.

Weatherheads

Voiced by: Eric Bauza (Gust-O) David Kaye (Shock-O) Jeff Bennet (Hail-O)

The Weaterheads are a trio of robots- Gust-O, Hail-O, and Shock-O -who first appear in "Riding the Storm Out." Initially disguised as human businessmen, they transform into skull-headed robots with bodies resembling business suits. All three claim not to possess emotions, though in reality they do, and have the power to manipulate various aspects weather; Gust-O manipulates wind and air, Hail-O manipulates ice and water, and Shock-O manipulates lightning and electricity. In "The Feels," they are also shown to be powered by negative emotions, hence they rampage through villages to replenish their energy supply Though they unleash powerful storms and a cyclone, they are eventually defeated after Ben tricks them into attacking each other.

They later return in "The Eleventh Alien" where they have formed an alliance with Vilgax. In exchange for dominion of the Earth, they use their powers to convince Ben that his latest alien, Shock Rock, is dangerously unstable and will destroy the planet. However, Gwen eventually uncovers their deceit, and later helps them realize that Vilgax has no intention of giving them the Earth. They then joined together into a three-headed, six-armed robot and attack Vilgax, only to end up being defeated again by Ben.

Alpha

Voiced by:

• Michael Emerson

Alpha is the main villain in the Ben 10-Generator Rex: Heroes United, an old Nanite creation of Caesar Salazar and the counterpart of the Omega-1 Nanite inside Rex.

Alpha was a very dangerous Nanite entity that could take over host bodies and control and absorb machines, by using the Nanites found within them. It was programmed by Caesar to think for itself so it could perform its original task: control the Nanites so they could do their job. However Alpha's energy form was unsustainable, every mechanical body it built burnt out extremely fast.

When it tried to take a biological body, Caesar was forced to use the equivalent to a Null Void Projector to fire Alpha into what he thought was an empty pocket dimension. However, unknown to Caesar, Alpha was sent to the Null Void, a penal colony created for intergalactic criminals, where it came into contact with alien technology that utilized a dimensional-equivalent to Nanites for power that it would use to return in pursuit of his "father" Caesar in order to become whole again.

However, something went wrong in the warp and he accidentally ended up in another world where he met and fought Ben Tennyson shortly before finally returning to his world but accidentally brought Ben into it as a result. When he arrived in New York, Alpha was curious about the existence of Nanites in the humans and creatures he saw, but was immediately attacked by Six before he could find out more from Caesar. The mechanical body he had acquired was immediately destroyed, severely wounding Six in the explosion as Alpha escaped in the confusion to continue his pursuit after Caesar. After Caesar refused to help him find a body that could sustain itself, Alpha instead went after Rex whose body contained an Omega-1 Nanite, potentially the only device in existence that could create a body that can sustain itself. Ben and Doctor Holiday were able to ward Alpha off, forcing it to seek an alternate source of Nanites. Alpha attacked the Bug Jar and absorbed every Nanite inside.

Craving for more power, Alpha hacked and copied the Ultimatrix and gave it the power to turn into EVO versions of Ben's aliens. With this, Alpha was able to grab Rex and absorb the Omega-1 Nanite in his body converting massive amounts of matter into more Nanites. After Rex was unable to use his Omega machines, Ben used Upgrade to merge with Rex, upgrade his machines and severely damage Alpha.

Following this skirmish, Caesar arrived on the scene and used a contraption to extract the Omega-1 from Alpha. Rex took control over Alpha's Nanites and compacted them into a baseball sized ball of extremely dense matter. Upchuck took the ball and dumped it into the Null Void on his way back to his own Earth. Inside the Null Void, Alpha's prison begins to crack open.

Black Knight

Voiced by:

• Jennifer Hale

Black Knight is a major antagonist from Generator Rex, having took over leadership of Providence from White Knight while Rex was momentarily displaced from time by Breach. She mostly appears near the beginning of Heroes United when Providence is trying to close a strange anomaly in the sky, but her communication with Caesar is interrupted by communication with White Knight.

V.V. Argost

Voiced by:

• Corey Burton

Vincent Vladislav Argost is the principal antagonist of The Secret Saturdays, which took place five years before the events of Omniverse. A highly intelligent Yeti who assumed a human guise to search for Kur, Argost became a long term enemy of The Secret Scientists and the Saturday family while funding his activities as host of the show Weird World. In the end, Argost was seemingly destroyed after he absorbed both Kur and the Anti-Kur which caused him to implode.

But in reality, expecting the possibility of such an event, Argost was trapped in a state of flux before he was revived by his associate Dr. Animo in the events of "T.G.I.S." While Argost was initially annoyed to find Animo modified him with traits of the Loch Ness Monster and Jersey Devil, he accepted his new form as he and Animo plotted to use the latter's Alien-Cryptid hybrid army to take over Bellwood. But the alliance soon fell apart and the Saturday family was able to free the cryptids from Animo's control with Argost drained of his essence, swearing revenge as he was taken away by Plumbers.

Frankencryptid

Frankencryptids are an army of mutant cryptids created by Dr. Animo for V.V. Argost.

Each one is a chimeric amalgamation of various cryptids. Argost was thrilled to learn that he still had the powers of the anti-matter Kur, which allowed him to control the entire army of mutant cryptids with a single thought. They attacked the Saturdays' airship, but were defeated by Shocksquatch. After their defeat, they were put into Plumber custody.

Chupacabra

Chupacabras are a type of cryptid from the planet Earth.

Eon

Portrayed by:

• Christien Anholt - Ben 10: Race Against Time

Voiced by:

• Yuri Lowenthal - Ben 10: Ultimate Alien (as Eon)
• Sean Donnellan - Ben 10: Ultimate Alien (as Alternate Ben)
• Judd Nelson - Ben 10: Omniverse

Eon is an alternate version of Ben that had gone rogue and wanted to eliminate all other versions of him. Eon is also a Codon Stream's DNA sample of a Chronian (a play on Chronos, Greek word for time) from the planet Chronia.

He was introduced in the first live-action movie Ben 10: Race Against Time within an alternate timeline. Eon has a plan to activate the "Hands of Armageddon", a Chronian artifact that exists throughout time and space, in many alternate timelines. He uses ape-like aliens to help him use the Omnitrix to turn Ben into a younger version of himself showing some control of the watch, due to the fact that the Hands of Armageddon needed the energy of a young Chronian to activate, he also deactivated the fail safe so his DNA would completely overtake Ben's personality, essentially changing him into a clone of himself and leaves the scene of the crime seemingly wiping himself from existence as "two of the same beings cannot exist in the same place at the same time". As Eon, Ben activates the Hands of Armageddon which will start an alien invasion, but returns to normal after Gwen manages to reach Ben inside young Eon. The real Eon appears again and tries to exact his revenge, but Ben manages to send him crashing into the Hands of Armageddon, destroying it in that timeline in a huge explosion.

Eon returned in the Ben 10: Ultimate Alien episode "Ben 10,000 Returns". It turns out that "Race Against Time" was in an alternate timeline. As it turns out, Eon survived his battle against the Ben of that timeline, and has since been traveling through various different timelines, enslaving versions of Ben wherever he finds them. When he comes to the real Ben (20 years from Ultimate Alien), Ben 10,000 sends him 20 years earlier to present day Ben. They eventually find out that he was absorbing the Bens, making them into his minions, and that he's a corrupt Ben Tennyson wanting to eliminate all other Bens and become the one and only Ben in the whole time-space continuum. They realized that Eon was hunting them from inside their Ultimatrixes. However, Eon was defeated when the Hand of Armageddon was destroyed with the Bens he absorbed sent back to their realities.

In the Ben 10: Omniverse episode "Ben Again", wanting to regain power over the multiverse, Eon switches Ben's mind with his younger version in a plan to take Paradox's Chrono Navigator before deciding to destroy reality when he learns he caused a temporal disruption. Luckily, Ben and his past self use their respective Clockwork forms to trap Eon between their timelines and undo the damage he caused. Eon later resurfaces in the "And Then There Was None"/"And Then There Was Ben" two-part episode, helping Vilgax recruit evil incarnations of Ben across the multiverse before being betrayed and then sent back to his reality. In the final arc of the Omniverse series, Eon helps Maltruant by providing him with Time Beast eggs for his plan to travel to time before the universe was created. However, Eon ends up being betrayed and sent back to his own dimension.

The Queen

Voiced by:

• Wendy Cutler - Ben 10: Alien Swarm
• Herbert Siguenza - Ben 10: Alien Swarm (in Victor's body)
• Tia Texada - Ben 10: Ultimate Alien (in Elena's body)

The Queen is a Nanochip, a biomechanical beings shaped like nano-chips from the "Hive Planets". The Queen produces the Hive from her body and later, after she takes up residence in Victor Validus's body she produces them from there; they have the ability to take over a person's mind. However, The Queen transferred herself into the body of Elena Validus after leaving a decoy queen in Victor that is destroyed by Nanomech.

In "Revenge of the Swarm", having fully integrated with her host's mind, the Queen influences Elena with her desires to keep Ben away from Julie in order to keep Ben all to herself. Ultimately, when she used the drones in an attempt to choke Ben to death, Elena was convinced by Julie to stop all this if she really loved Ben and took control over herself for a moment to sacrificed herself to destroy the Hive. However, the Queen survived as she and the Hive constructed a new body in Elena's likeness. Acting on Elena's feelings for Ben during the events of "The Perfect Girlfriend", the Queen attempts to steal him by assuming Julie's form. However, seeing that she knows nothing about love, the Queen resolves to hate Ben instead and vows revenge on him.