Nyxthid, Shifting Veil

Flying

Mutate {b}{b}{b}{b}{b}{b} (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 the abilities under it)

The first time this creature mutates on during your turn, search your library for X number of cards, where X is the number of times this creature has mutated. Put those cards into your hand, then shuffle.