The rules

Upon entering the Quindecim bar, the deceased have the rules told to them by Decim (and later his assistant as well):
 * 1) He is unable to tell them where they are.
 * 2) The two of them will now play a game.
 * 3) The Game will be chosen by roulette.
 * 4) The two will stake their lives on The Game.
 * 5) They cannot leave until the game is over.