Tri-chess

Tri-chess is the name of a chess variant for three players invented by George R. Dekle Sr. in 1986. The game is played on a board comprising 150 triangular cells. The standard chess pieces are present, minus the queens, and plus the chancellor and cardinal compound fairy pieces per side.
Tri-chess was included in World Game Review No. 10 edited by Michael Keller.

Game rules

The illustration shows the starting setup. White moves first and play proceeds clockwise around the board. When a player is checkmated or stalemated, their king is immediately removed from the game and their remaining pieces become under control of the player delivering the checkmate or stalemate. Pawns of appropriated armies do not change their direction of movement toward promotion. The last surviving player wins the game.

A bishop moves as the bishop in the tri-chess two-player game.
A rook moves as the rook in the tri-chess two-player game.
A knight moves in the pattern: two steps as a bishop, then one step as a rook in an orthogonal direction. A knight leaps any intervening men.
The chancellor moves as a rook and knight.
The cardinal moves as a bishop and knight.
The king moves as the king in the tri-chess two-player game. The king slides cells whether castling "cardinal-side" or "chancellor-side".
A pawn moves and captures as a pawn in triangular chess.