The Black Knight

When the only other players are the king and
their teammates, reveal this role and you all win
the game.
When there is no King, if The Black Knight is
face down you lose the game.
If you would lose the game any other time, reveal
The Black Knight instead remove all commander
damage and poison counters. Your life total
becomes 10. While The Black Knight is revealed,
the king becomes your opponent.
When you have no opponents, you win the game.