The nightrider, alternatively spelled knightrider and also known as the knightmare or unicorn (though the latter term sometimes refers to 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 an altered version of the knight's icon.
The nightrider, like the knight, can jump over blockades in closed positions and is good at delivering forks.
This is because, unlike the knight, the nightrider can gain a tempo.
Nd2# With nightriders on the board, a mutual discovered perpetual check is possible.
In the diagrammed position, 1...e5 2.fxe6+ (capturing en passant) results in triple check.