Basically it's a tournament where everyone is in pairs. I don't mean everyone controls two characters. I mean literally you have to work WITH another player.
One thing that annoys me about roleplay is that there's only very rarely people who know how to work together, everyone wants to be big man on campus, this would be a nice little exercise in cooperative play.
the basic plot is that there are 12 humans who inherited the genes of the Incubus king (how this happened exactly will be explained if there is enough interest) and each possess a 'King Piece' inside them which corresponds to each kind of piece on a chess board (so black pawn, white pawn, black king, white queen etc). their piece determines which part of the incubus king's power they inherited.
In order to do battle each king candidate needs his own 'queen'. this queen is any woman that the king candidate had sexual intercourse with and, using his seed, turned into a succubus. Whether the queen is his lover, or just some hooker he happened to be with when his powers awoke, or a girl he raped, she is now bound to him and incapable of refusing his orders or harming him (not to say that she is inherently 'loyal' to him, simply that she is bound to his service).
so how it goes is that one player is the king, the other is the queen. the queen is the one with all the real supernatural powers, and the king is, by comparison, quite weak (just like in chess where the queen is the most powerful piece and the king is second only to the pawn in weakness). the tourney will be fought in battles of 2 on 2 and will end only when one of the kings is dead (a king can live without his queen, but a queen will die with her king).
as you defeat more and more people of your color you will absorb their pieces and add their powers to your own until one fighter for white and one fighter for black remain (though you can still fight and kill people of the other color so as to make the final battle easier for you, you will still absorb their piece you just won't be able to use their power). the winner is crowned the new King Incubus.
so, any takers?