Dirge Bat is a rare Creature — Bat card from Magic Online Promos (PRM), collector number 80997.
Mutate {4}{B}{B} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.) Flash Flying Whenever this creature mutates, destroy target creature or planeswalker an opponent controls.