The Kingsguard

You are a Knight (The King and his teammates are
your teammates. When your team are the only players standing, reveal your role and you all win the game.)
When there is no King, you lose the game.
If combat damage dealt from unblocked
attacking creatures could cause the King to lose
the game, you may reveal The Kingsguard. If you
do, prevent all combat damage that would be
dealt this turn.