Crovax the Cursed

Crovax the Cursed enters the battlefield
with four +1/+1 counters on it.
At the beginning of your upkeep, you may sacrifice a creature. If you do, put a +1/+1 counter on Crovax. If you don't, remove a +1/+1 counter from Crovax.
{b}Black: Crovax gains flying until end of
turn.