Xorvintaal
Xorvintaal, or "The Great Game", is a game played by dragons in the Dungeons & Dragons multiverse. Invented in the Monster Manual V for Dungeons & Dragons 3rd Edition, Xorvintaal can perhaps be most simply described as a draconic version of chess crossed with poker, or Paradox-Billiards-Vostroyan-Roulette-Fourth Dimensional-Hypercube-Chess-Strip Poker; players take the role of masters who use the world as their board and non-dragons as pieces, wagering treasure and territory in subtle gambits they enact through their armies of servants. To keep things on a level playing field, dragons who agree to partake in Xorvintaal undergo a magical ritual that permanently strips them of their innate spellcasting powers as well as their ability to break the rules of the game, but grants them the ability to create and empower pawns, as well as to derive unique mystical abilities by winning victories in the Game. It's unclear if this means Arcane Dragons are exempt from being players. Taking years to learn and centuries to master, Xorvintaal exemplifies the more "social" aspect of the D&D dragon.
As a monster, Xorvintaal is broken into two creature templates; one for the dragons who play it, and one for creatures who have been chosen as exarches, or the trusted commanders who directly serve each player.