Auspicious Starrix is a uncommon Creature — Elk Beast card from Ikoria: Lair of Behemoths (IKO), collector number 294. Current market price: $0.34 (foil $0.41), TCGplayer market prices via Scryfall.
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.