Kai Chisaki, Crazed Remaker

Mutate {3}{b}{r} (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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Creatures you control have mutate. The mutate
cost is equal to their mana cost.
When this creature mutates, put X +1/+1
counters on this creature, where X is its power