Solemn Crusader

When Solemn Crusader enters the battlefield, choose a color. Whenever Solemn Crusader blocks or is blocked by a creature of the chosen color, it gains first strike until end of turn.
Whenever Solemn Crusader attacks, each other attacking creature gets +1/+0 until end of turn.
When Solemn Crusader dies you may pay {r}{w}. If you do, exile it instead and deal 4 damage to target opponent. You gain 4 life.