In Sovereign Chess, castling still plays a role, although perhaps with different objectives. A larger board doesn't give the King as much protection as traditional chess, and movement by the rook pawns often exposes those positions to which a king might retreat. However, such move can free a rook for battle into the center area of the board, and is occasionally employed.
To clarify Rule #14, it may be helpful to define "applicable" pieces to castle. Like traditional chess (Rule #1) castling may only be executed:
- Between a king and a rook, neither of which has moved during the game,
- When all squares between the two pieces are free,
- When the king is not in check, and
- When the move does not place the king into, or through, check.
Figure 25: Typical Pre-Castling Position with Possible Castling Options
The one difference Rule #14 does identify is how castling takes place. Instead of moving the king two squares toward the rook, the king may move to any open square between the two pieces.
The diagram at left shows the possible castling options that White can make.
The other difference in castling--unique to Sovereign Chess--is the ability to castle with a "controlled" rook; that is, one that does not match the color of the player's king. Since the rook can not have moved, and must be located on the back row of the board, this means that White can castle with either Pink or Green, while Black can castle with Violet or Yellow.
Assuming White has control of Pink, and all other conditions are satisfied, Figure 26 shows a possible castling sequence for White.
Figure 26: Possible Castling Sequence for White with Pink Rook
Sovereign Chess just wouldn't be complete without Rule #15...