Nightrider (chess)

A nightrider (also known as a knightmare or unicorn, though the latter sometimes also means the bishop+nightrider compound) is a fairy chess piece that can move any number of steps as a knight in the same direction. The nightrider is often represented by a symbol similar to the knight's icon, but altered in a way to indicate the additional straight-line motion.[1] In this article the nightrider is represented with an inverted knight, and notation N (in which case the knight is abbreviated as S for German Springer).

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Nightrider (represented by an inverted knight) makes any number of knight moves in the same direction.

The nightrider was invented by T. R. Dawson in 1925, and is often used in chess problems.


Movement

The nightrider moves any number of steps as a knight in the same direction. Intervening squares must be vacant. For example, a nightrider on b2 can reach square c4 and forward to d6 and e8, but cannot jump over the f4-pawn to reach h5.

Examples
T. R. Dawson
British Chess Magazine (1925)
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#5 (Nightrider c6)


The king together with two knights cannot win the endgame against a lone king (KSS vs. K), but the king together with a knight and a nightrider can win, because the knight cannot gain a tempo, but the nightrider can.

Solution: 1. Ne7! Ka7 2. Ng3 Ka8 3. Ne4 Ka7 4. Sb5+ Ka8 5. Nd2#

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Mutual discovered perpetual check with nightriders

With nightriders on the board, a mutual discovered perpetual check is possible.

A possible continuation would be: 1. Kd3+ Kc5+ 2. Kc3+ Kd5+ 3. Kd3+ Kc5+, etc.

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After Black moves his pawn to e5, taking it en passant results in triple check.

Nightriders can also participate in triple check.

References
  1. Piececlopedia: Nightrider at The Chess Variant Pages

Bibliography

  • Hooper, David; Whyld, Kenneth (1992), The Oxford Companion to Chess (2nd ed.), Oxford University Press, ISBN 0-19-280049-3
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