A nightrider is a fairy chess piece

Fairy chess piece

A fairy chess piece or unorthodox chess piece is a piece analogous to a chess piece. It is not used in conventional chess, but is used in certain chess variants and some chess problems...

 that can move any number of steps in a direction that a knight

Knight (chess)

The knight is a piece in the game of chess, representing a knight . It is normally represented by a horse's head and neck. Each player starts with two knights, which begin on the row closest to the player, one square from the corner...

 can move. For example, a nightrider on b2 can reach square c4 and forward to d6 and e8, but cannot jump over pawn f4 to h5. The nightrider is usually represented by an inverted knight on diagram and symbol N in text, in which case the knight

Knight

A knight was a member of a class of lower nobility in the High Middle Ages.By the Late Middle Ages, the rank had become associated with the ideals of chivalry, a code of conduct for the perfect courtly Christian warrior....

 is abbreviated as S for German Springer. Nightrider was invented by T. R. Dawson in 1925. Nightrider is used mostly in chess problems.

Nightrider can also give triple check

Double check

In chess, a double check is a check delivered by two pieces at the same time. In chess notation, it is often symbolized by "++".-Discussion:...

.

Example

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

Tempo (chess)

In chess, tempo refers to a "turn" or single move. When a player achieves a desired result in one fewer move, he "gains a tempo" and conversely when he takes one more move than necessary he "loses a tempo"...

, but the nightrider can.

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

With nightriders on the board, a mutual discovered perpetual check

Perpetual check

In the game of chess, perpetual check is a situation in which one player can force a draw by an unending series of checks. Such a situation typically arises when the player who is checking cannot deliver checkmate; while failing to continue the series of checks gives the opponent at least a chance...

 is possible.
Then a possible continuation would be: 1. Kd3+ Kc5+ 2. Kc3+ Kd5+ 3. Kd3+ Kc5+ etc.

External links

• Nightrider problems on PDB Server