Sidisi's Pet is a common Creature — Zombie Ape card from Khans of Tarkir (KTK), collector number 90. Current market price: $0.05 (foil $0.28), TCGplayer market prices via Scryfall.
Lifelink (Damage dealt by this creature also causes you to gain that much life.) Morph {1}{B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)