Boneyard Lurker is a uncommon Creature — Nightmare Beast card from Magic Online Promos (PRM), collector number 80963.
Mutate {2}{B/G}{B/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, return target permanent card from your graveyard to your hand.