Ethrunn, Terror Incarnate

Mutate {3}{u/b}{u/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.)

Deathtouch, menace
Whenever this creature mutates, you may discard
a card. If you do, Ethrunn, Terror Incarnate deals damage to any target equal to the discarded card's converted mana cost.