Ehdirra, The Necromancer

{b}{w}{g}, Sacrifice any number of zombies:
For each zombie creature sacrificed this way, put a +1/+1 counter on a target creature.
Whenever non zombie creature dies you
may remove two +1/+1 counters from Ehdirra, The Necromancer. If you do,
create a 2/2 black zombie creature token.