Crota, Son of Oryx

Trample, Convoke (Your creatures can help cast
this spell. Each creature you tap while casting this
spell pays for {1} or one mana of that creature's color.)
Oversoul - Crota, Son of Oryx enters the
battlefield with 6 oversoul counters on it.
Whenever a creature your opponent controls is destroyed by combat, remove an oversoul
counter from Crota. When Crota reaches 0
oversoul counters, you win the game.