Janus Chess is a chess variant played on a 10×8 board. It features a new piece, the Janus (also known as archbishop or cardinal), with the combined moves of a bishop and a knight. This piece is named after the Roman god Janus because this god was usually depicted with two faces looking in opposite directions. Janus Chess was invented in 1978 by Werner Schöndorf from Bildstock, Germany.
The usual set of chess pieces is extended with two pawns and two Januses per player. Each Janus is placed between a rook and a knight. The relative position of the king and queen is reversed compared to chess. After castling the king is placed on either the b-file or i-file and a rook is placed on either the c-file or h-file, depending upon which side to castle is chosen.
Note that the Janus is the only piece in this game which is able to checkmate the opponent's king without the assistance of any other piece, if the king is in a corner.