Doppleganger

No, I'm the Sheriff — At the start of the game, set
your life to X, where X is the Sheriff's life total.
If your life total would reach Y, where Y is the
difference between X and the normal starting
life total, you lose the game.
(Start the game with "fake" life total).
If the Sheriff would lose the game from a source
you control, or is the only remaining
player, you win the game.
If you lose the game, reveal your role.