Primalbringer

Mutate {7}{g}{g} (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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Spend only mana from creatures to cast or
mutate this creature.
Whenever this creature mutates, creatures you
control get +X/+X and trample until end of
turn, where X is this creature's power.