Pippalada
Pippalada was an ancient Indian Vedic sage and philosopher in Hindu tradition. He is known to have written the Prashna Upanishad, which is among the ten Mukhya Upanishads. He was the son of noble benevolent sage Dadhichi, who donated his bones to the devatas to provide them a material for making weapons and defeat the Asurs. He was the founder of Pippalada School of thought, which taught the Atharvaveda.
Birth
At the time his father Dadhichi gave up his life to donate his bones to [Indra] and help him defeat the asur Vritra, his wife Swarcha was pregnant with Pippalada. When Swarcha came to know about death of her husband, she placed the infant Pippalada under a pippal tree. Then she committed suicide to reunite with her husband. The infant Pippalada was taken care of by Dadhichi's sister, Dadhimati. He helped himself to the pippal leaves and amrit(nectar) given by Chandra dev (God of moon).
Revenge with Indra
When Pippalada grew up and came to know about the way his parents died, he performed a heavy penance to Lord Shiva and obtained a demon to kill all the devatas. All the devatas went to Shiva for protection. Shiva made Pippalada realize that nothing can be gained by killing the devatas as it will not bring his parents back.
Defeating Shani
Pippalada out of revenge for Lord Shani for giving tortures to his father Dadhichi, he obtained Brahmadanda and hit Lord Shani on his foot . It was then Lord Shiv who made Pippalada of his wrong doings n explained that Lord Shani just did his duty and it was the wrong deeds of Dhadhichi due to which he was punished.
Prashna Upanishad
The following six sages: Kabandhin Katyayana, Bhargava Vaidarbhi, Kausalya Asvalayana, Sauryayanin Gargya, Saibya Satyakama and Sukesan Bharadvaja approached Pippalada asking him about purpose of life. They performed austerities for a year and asked six questions. These questions and answers later came to be known as the Prashna Upanishad.