Sovereign Chess is a two-player game, Black versus White, but with armies of ten different colors located around the board. These pieces are neutral, and can not be moved or captured until one of the players land on a square of the matching color. Multiple armies can be controlled by landing on many different colored squares, or by a chain of control.
Since pieces in Sovereign Chess move like traditional chess, there is not a steep learning curve. There are only minor adjustments for movement, given the size of the board, and rules that govern the control of additional armies. If you already know how to play chess, it usually takes about 5 minutes to learn Sovereign Chess, whether you're 6 or 66!
You can find a great tutorial video on the rules and how to play here,
Contents include rules for standard Sovereign Chess and Royale Mode, 16x16 square folding Sovereign board, and 140 chess pieces.