Unholy Sacrifice

{t} Sacrifice target creature you control, summon a 0/1 black zombie token, with, defender, when this card dies destroy target creature and, at the beginning of your upkeep put a +1/+1 counter on this creature.
When this creature has 4 or more +1/+1 counters on it, it loses defender.
When this card has 7 or more +1/+1 counters on it, sacrifice it, but destroy an extra target creature.