Pole Chess is F.I.D.E. chess with a piece added for either side: the Poles. It was first described by writer Piers Anthony in his science-fiction / fantasy book "Robot Adept" (1988). The book describes a match between two players, one in the scientific world of Proton, the other in the magical world of Phaze.

The Poles start the game off the board to either side. They can be "invoked" anytime after the first piece is lost on either side. It can go to any unoccupied square on the board in one move. It can neither take nor be taken (except for the mysterious "Pole-capturing" rule); it can only block. A pawn cannot promote to a Pole.

The game is won by checkmating your opponent's King or by your opponent resigning. The rules for drawing a game are as for F.I.D.E. Chess. Apart from rules involving the Poles, the rules and movement of pieces are unchanged.

Piers Anthony's book said "The pole could neither take nor be taken, except in one very special circumstance." This special circumstance was not described further in his book, he apparently never worked it out. This has led to speculation about the mysterious "Pole-capturing" rule.

This Zillions rules-file opens with a default version with no "pole-capturing" rule. There are also nine variants each with a different "pole-capturing" rule:

VARIANT ONE: The King may take the enemy Pole if it is in check and it has no other move.

VARIANT TWO: You may take the enemy Pole if you are in check.

VARIANT THREE: Your King may take the enemy Pole.

VARIANT FOUR: You may take the enemy Pole with any piece if it is next to your King.

VARIANT FIVE: A Pole may suicide-capture the enemy Pole with a King-move.

VARIANT SIX: A Pole may take the enemy Pole with a King-move, but can be captured normally from then on.

VARIANT SEVEN: If a Pole gives discovered check, it may be captured normally from then on.

VARIANT EIGHT: A Pole can capture and be captured if your King is in check and has no other move.

VARIANT NINE: Your Pole may suicide-capture the enemy Pole if by so doing you will "bare" your king.