Grant Acedrex

Grant Acedrex is a medieval chess variant dating back to the time of King Alfonso X of Castile. It appears in the "Libro de los juegos" of 1283.
Rules.
The following rules are from the reconstruction given on the website of Jean-Louis Cazaux, based on work by him and Sonja Musser. The game is played on a 12×12 board.
Castling does not exist in "Grant Acedrex". On its first move, however, a king may make a diagonal or orthogonal leap of two squares (Betza notation AD) in addition to its normal moves.
Using dice.
The game could be sped up by using eight-sided dice to dictate which piece could move that turn, ranking them in the order: king (8), aanca (7), unicornio (6), rook (5), lion (4), crocodile (3), giraffe (2), and pawn (1).
Computer players.
The multi-variant Chess engines Fairy-Max and Postduif can play Grant Acedrex under the XBoard or WinBoard user interface.