Multi Player Chess
1. Setup
An identical chess set is required for each player involved. For tournament games, each chess set should be numbered, and each chess piece should be labeled underneath with its originating set.
For the purposes of this description, 4 players (A, B, C, D) and 4 chess sets (1, 2, 3, 4) will be used; however, any number of players/sets, 3 or more, can be used.
Set up each of the four players playing white versus one player and black versus another player as in the diagram (the rectangles represent playing colors).
If clocks are used, set up the four clocks with twice the normal playing time (e.g., if your players normally play 30-minute clocks, set the clocks to 1 hour).
2. Play
Each player plays according to the normal rules of chess (with exceptions noted below) versus two players simultaneously (one game as white, the other as black).
Each player keeps all pieces captured in a stockpile for further use (see below).
The moment any player calls checkmate against a player, all games are temporarily halted. The player who has just lost is eliminated from the circle, including their stockpiles and the board the losing game was played on. The circle is then closed in—the game still in play by the eliminated player is taken over by the winner of the just-lost game (e.g., if B lost their game against A, B is eliminated along with their stockpile; then A commences playing the game which was being played between B and C. A brings their stockpile into that game).
If multiple players call checkmate simultaneously, then the above process is repeated for each player.
The winner is the player remaining after all other players have lost one game.
If all remaining players call checkmate simultaneously, the result is a draw between all players.
3. Stockpiles
Each player keeps white and black pieces taken from both games in a stockpile. The stockpile is used to reinforce your position in the game you're playing against another player.
Pieces can only be placed on the board in their starting position.
The King cannot be stockpiled.
A piece cannot be placed on a board to counter a checkmate; however, it can be used to counter a check.
A piece from a given board cannot be replaced on that board; that is, a rook from board 1 that moves around the board to be in the stockpile of a player on board 1 is removed from the game (for simplicity of setup, this rule can be ignored in social games).
A piece cannot be placed in such a way as to introduce an illegal situation, although it can be placed in such a way to achieve what appears to be an 'unachievable' situation.