Attribute modifiers for standard pieces for fun and profit

These could be applied to any piece before the match, by agreement between the players, symmetrically. Could be applied to individual pieces ("the b-knights are resilient"), or by type ("all bishops are poisoners"). Probably not all of them are feasible to work with, but there are some ideas how to liven up the game and expand the variety of matches.

- Demoter: Instead of capturing a piece, demotes it to a pawn. A bad blunder with this one could lead to checkmate on one's own move.

- Resilient: Has several "lives" and must be captured multiple times before it's removed from the board. Alternatively, must be attacked by multiple pieces simultaneously in order to be captured by any of them.

- Poisoner: Instead of capturing a piece directly, marks it to die after several turns have passed. Does not move from its square when poisoning the target piece.

- Duelist: Can only capture and/or be captured by either the same piece type, or the king.

- Taunter: If this piece actively moves onto a square that is under attack by an opposing piece, it must be captured on the opponent's next move unless doing so would expose the king to a check. If multiple opponent's pieces attack the same square, announce which one is being taunted. If attacked normally by an opponent's move, this doesn't happen, the taunt can only happen as part of its own move.

- Demolisher: Remove this piece from the board to destroy the square it is standing on - no piece can move onto that square or attack across it until the end of the match. Knights can still jump over it. (Not wise to apply this to all pawns)

- Warper: When this piece is captured, the capturing piece must return onto its starting square, or closest possible square to it if the starting square is occupied.

- Backstabber: Every time this piece makes a capture, it changes color.

- Invisible: This piece is invisible. Announce when you move it, but not where you're moving it to. If the move causes an effect (check, capture, or blocking a castle move), the effect must be announced.

Very nice ideas. You'll find some of them here.