Omega Chess is a commercial chess variant designed by Daniel MacDonald in Toronto. The game is played on a 10x10 board with an extra square in each of the extreme corners where the wizards are placed at the start of the game. The game is laid out like standard chess with the addition of a "champion" in each corner and a "wizard" diagonally behind each champion.
Part of the reason for adding the new pieces was to equalize the number of jumping pieces with sliding pieces. The wizard was created specially to be a color-bound piece, a parallel to the bishop. Because of the symmetry and four additional corners, Omega Chess creates new tactical possibilities, including the possibility of checkmate with two knights.
Omega Chess has garnered endorsements by grandmasters Michael Rohde and Alex Sherzer.
The normal rules of castling apply. Also, it is done exactly as in chess, with the king moving two squares to either side: to h0 for White or h9 for Black to castle kingside, and to d0 or d9 to castle queenside. (See diagram.)
As seen in the diagrams, the ranks are numbered 0-9, and the corner squares behind a0, j0, j9 and a9 are notated w1, w2, w3 and w4 respectively. It should be noted that these squares are part of the board, and all pieces (except rooks and pawns) can enter them. (See the problem at the end of the page.)
1.f4 d5 2.Nd2 Ng7 3.Wa2 Cc7 4.Ng2 f7 5.Wj2 Wa7 6.e4 de4 7.Ne4 Bb4+ 8.Be1 Nd7 9.c3 Be7 10.Wi5 0-0 11.d4 Cc6 12.Bd3 b5 13.b4 Wd6 14.Cc2 Wj7 15.Ch2 Wi4 16.Nh4 Wh5 17.Wd1 We3+ 18.Kg0 c7 19.i4 Wg4 20.Be2 Wd5 21.Rc0 Bb7 22.Nc5 Black is aiming a lot of artillery at the white king. Perhaps White should follow suit and play this knight to g5 instead of c5. 22...Nc5 23.bc5 Qd8 24.Qh3 Wh4 25.Bh4 Either on this move or the next, recapturing with the champion looks more promising. 25... Bh4 26.Wh4 Ch7 27.Wg2 Ce4 28.Ce4 We4 29.Qj3 j7 30.i5 i6 31.Wg7 hg7 32.Ri3 Ki8 33.Qj4 Rh9 34.Rj3 Ci7 35.Re0 Qf6 36.Bc0 e6 37.Bb1 Wf5 38.Wf5 ef5 39.Re8 Rh8 40.Rje3 g6 41.Qi3 Qg7 42.j4 (see diagram) 42...b4! Black seizes the initiative. 43.R8e5 bc3 44.Rc3 Bh1 45.Kh1 Rb1 46.Ra3 Ch7 47.Ra8 Ch5 48.Ra9 Qh7 49.Ree9?? Cj3! 50.Qj3 Qh2+ 0-1
1.f4 f5, 2.Bc4 Bc5, 3.Qj5 Ng7?? (defending the pawn on f5) 4.Qxg8#
1.Wa2 Ng7, 2.Wb5 Ni6?? 3 We6#
The four corner squares in Omega Chess offer many endgame possibilities and peculiarities. For example, if you have two rooks, a bishop and a wizard against a lone king, you cannot win if the bishop and wizard attack one color, with the enemy king being on a corner square of the other color. This leads to the inevitable question of what combinations of reduced material can deliver mate.
Unlike in standard chess, a lone queen (without the king's assistance) can force mate. As well, two rooks find it easy to mate provided the enemy king is not in a wizard or champion starting square.
In the position on the left, White is obliged to check the enemy king back to the edge of the board, since Black isn't going to go there voluntarily. 1.Rd8+ Ke9 2.Ke7 Kf9 3.Kf7 (The white king must pursue the enemy king because when Black gets to i9, the white king wants to be on h7, controlling i8 so the rook can check on d9, forcing the king to j8, followed by Re8 - Kj7, Rj8#) 3...Kg9 (Not 3...Ke8 because of 4.Rd6 Kf8 5.Rd8#) 4.Kg7 Kf9 it is safe for the black king to double back. If the rook was on e8, then it could just retreat along the file and deliver mate next move. Or if it was on any other rank, it could now move to the e-file, but as it is the rook would be vulnerable to capture.
Two bishops can deliver mate fairly easily, as can two knights, although in the latter case the task of herding the enemy king into a corner requires a lot of patience.
Two champions mate easily and so do a champion and a knight. A bishop with a wizard on the opposite color squares can also force mate although technique is involved since the enemy king has to be driven into the same colored corner as the bishop. However two wizards can't force mate. A rook in combination with either a knight or a champion can force mate easily and, provided the enemy king is not on the wrong colored wizard's square, (or corresponding champion's square) then both rook and bishop, and rook and wizard are also easy wins.
In the remaining combinations of material, bishop and champion, champion and wizard, bishop and knight, and knight and wizard, the requirement for winning is that the enemy king should be kept out of the wrong colored corner since the knight alone, or the champion alone cannot defeat the king. Having met this requirement, the mating technique for bishop and champion, and wizard and champion are fairly straightforward, while the technique for bishop and knight is somewhat more complicated. As for knight and wizard, it is possible to set up positions in which the enemy king is corralled, leading to checkmate, but there doesn't seem to be a way of forcing these positions.
In 2008, the authors of Omega Chess developed an extension to the game called Omega Chess Advanced.