In Basilisk Chess the rules are the same as in orthodox chess, except that one extra piece per player, a Basilisk, is placed in the reserve. After having jumped any piece, the Basilisk cannon can slide and capture like a queen. However, if no jump move exists it's allowable to slide like a queen, but without capturing.

Enemy pawns, however, can restrict its movement. The Basilisk can only reach the square immediately behind the enemy pawn, regardless of direction. By example, if the black king is checked on the g-file, it can defend itself by moving the pawn forward. While its tactical capacity is truncated the Basilisk can harmonize with the positional qualities of the game. Positioned two or more steps behind a friendly pawn, it can threaten an enemy Basilisk, which cannot threaten back. This is an important positional aspect. The Basilisk has about the same value as bishop + pawn (preliminary estimate).

Before starting, the players must decide whether they want to use the extra piece. To make a decision, press on the little black square. Only if both players choose not to use the extra piece, then it becomes a regular game of chess. If white turns down the extra piece, then black can overrule this.

If players have elected to include external pieces, they may either move a piece or pawn, or drop the extra piece from the reserve. Pieces may only be dropped on the first rank, on an empty square behind a friendly pawn. The friendly pawn is immediately relocated one square ahead, to a position which must be empty. If these conditions aren't satisfied then the piece cannot be dropped. Should a player refrain from inserting his extra piece at these occasions, then he has forfeited his chance of introducing it. Note that pieces and pawns are allowed to move before the extra piece has been dropped. You are allowed to make a pawn-relocation if in check, if the pawn-relocation covers the check.