Regal Leosaur (202) [Ikoria: Lair of Behemoths]

Mutate {1}{R/W}{R/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.) Whenever this creature mutates, other creatures you control get +2/+1 until end of turn.