Vadrok, Apex of Thunder [Ikoria: Lair of Behemoths Prerelease Promos]

Mutate {1}{W/U}{R}{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.)
Flying, first strike
Whenever this creature mutates, you may cast target noncreature card with converted mana cost 3 or less from your graveyard without paying its mana cost.