Cunning Assassin

Flash, Skulk
Ambush--Whenever Cunning Assassin or another permanent with Ambush enters the battlefield under your control, you may pay {u/b}{b}. If you do, destroy target creature that was dealt damage this turn.
Revolt--When Cunning Assassin enters the battlefield, if a permanent you control left the battlefield this turn, add {u}{b} to your mana pool and Cunning Assassin deals 1 damage to target creature.