Traitor Chess

This variant was invented in January 2000 by Joao Pedro Neto. The main idea is to insert some temporary imperfect information into chess, and also give to the players a little of paranoia about their own pieces.

Rules

1. The FIDE rules apply, except in the following:
2. A traitor is a non royal piece of the enemy.
3. The pieces have the following values: Queen/9, Rook/5, Bishop/3, Knight/3, Pawn/1.
4. Before the game starts, each player has 9 points to choose one or more traitors and writes them down on a paper (see note). Each player should indicate specific pieces. See the sample game for examples.
5. Before his turn, each player can announce one of his remaining traitors, and thus controlling it (i.e., the other player cannot use the announced traitor anymore).
6. A traitor does not change its color. All that changes is which player can control it. As in regular Chess, pieces of the same color cannot capture each other, and opposite colored pieces can capture each other. Regarding the traitor pieces under your control, they can:
   1. Capture your own pieces
   2. Check your own King
   3. Capture traitor pieces controlled by your opponent
   4. Block your opponent's regular pieces, because these pieces cannot capture them
   They cannot:
   1. Capture your opponent's regular pieces
   2. Check your opponent's King

notation: I use (T-piece) to represent traitor announcement.

note: For net play, each player can send an encrypted file (e.g., zip or word file) with the traitor information. At the end of the game each player sends the key to the encrypted file. In this way, it is possible to check the information.

Sample Game

[White Traitors: Rh1,Bc1,g2]
[Black Traitors: Qd8]

1. e4 e5
2. Nf3 Nf6
3. Bc4 Ng4
4. 0-0 Bc5

5. Nc3 (T-Rh1)N:f2 [The Rh1 traitor was announced! Black may use the traitor anytime!]
6. Qe2 Ng4+
7. Kh1 (T-g2)Rg1 [Now, White cannot move the Rook and the g2 Pawn]  

8. Ne5 Bb6
9. N:e5 0-0
10.Qf3 Qe7
11.(T-Q)B:f6+ [Time for White attack]

11... R:f7
12.Q:f7 Kh8
13.Qg8++ 1-0

Variants

Simplified Traitor Chess

Created by Fergus Duniho in March 2000. In this variant, players write down pieces names but do not specify exactly which pieces will become traitors. For example, a player could write down "1 Knight, 1 Bishop, and 3 Pawns." The player would then decide during the course of the game which Knight, Bishop, and Pawns would become traitors.

Impromptu Traitor Chess

Created by Fergus Duniho in March 2000. In this variant, players do not write down any pieces at the start of the game. Instead, players decide during the course of the game which pieces will become traitors. Each player is limited to a total of nine points for the pieces he can turn into traitors.

Defector Chess

Created by Joao Pedro Neto in January 2000. In this variant, traitors change color when they are announced, completely defecting to the other side. To make the game playable, Defector Chess includes the following additional rule:

• A piece may not change sides if it will check a King.

Without this rule, White could make the Black Queen defect and take the Black King on the very first turn.

• A player cannot immediately undo a defection by making the same piece defect back on the next turn.

However, the cost of undoing a defection might be enough to discourage players from regularly doing it. When you undo a defection, you lose some of your ability to make new pieces defect. So it would also be interesting to play Impromptu or Simplified Defector Chess without this rule.

Double Agent Chess

Created by Fergus Duniho in March 2000. In this variant, traitor pieces (now called double agent pieces) can be moved by either player. A weak Ko rule is added, which says that a player may not undo his opponent's last move by moving the same piece back to the space it just moved from. Although double agents can be controlled by either player, they are still limited to capturing pieces of the opposite color. Simplified and Impromptu versions of this variant are also possible.

Defector-Double Agent Chess

Created by Fergus Duniho in March 2000. In this variant, which combines Defector Chess and Double Agent Chess, a piece changes color when it is declared to be a double agent. The additional rules of Defector Chess and Double Agent Chess all apply to this game. Simplified and Impromptu versions of this variant are also possible.

Mercenary Chess

Created by Fergus Duniho in March 2000. In this variant, players may turn enemy pieces into mercenaries. Mercenaries may be moved by either player and may capture pieces of any color, including other mercenary pieces. The weak Ko rule from Double Agent Chess is included in this variant. There is also a rule, adapted from Defector Chess, which says that you cannot turn a piece into a mercenary if it will put the enemy King in check. Simplified and Impromptu versions of this variant are also possible.

Equipment

Traitor Chess and its variants are best played with two Chess sets which are different in design, size, or color. One set can be used for regular pieces, and the other set can be used for traitor pieces. For Mercenary Chess, the same color may be used for all the mercenary pieces, though it isn't important whether or not you do it that way.