Ervira, Peak of Evolution

Mutate {4}{r}{g}{w} (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.)
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Trample, haste
Whenever this creature attacks, put a +1/+1
counter on it for each time it has been mutated
this game.