Goth, Terror of the Skies

Flying
Deathtouch
Sacrifice a creature: Goth, terror of the Skies is unblockable this turn. Whenever a creature dealt damage by Goth, terror of the Skies leaves the battlefield, put a +1+1 counter on each bat you control. Whenever this creature leaves the battlefield you may pay {b}{b}{b}. If you do, return Goth, Terror of the Skies to the battlefield under your control.