Auspicious Starrix

—Mutate {5}{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.)
Whenever this creature mutates, exile cards from the top of your library until you exile X permanent cards,
where X is the number of times this creature has mutated. Put those permanent cards onto the battlefield.