Kaszca, Agent of the Undead

Petrify (Whenever a creature blocks or becomes blocked by this creature, put a petrify counter on that creature at end of combat. It can't attack or block for as long as it has a petrify counter on it.)
{b}{g}{u}, {t}: Destroy target creature with a petrify counter on it. Amass X, where X
was the number of petrify counters on that creature.