Pearl Lake Ancient is a mythic Creature — Leviathan card from Khans of Tarkir (KTK), collector number 49. Current market price: $0.47 (foil $1.19), TCGplayer market prices via Scryfall.
Flash This spell can't be countered. Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.) Return three lands you control to their owner's hand: Return this creature to its owner's hand.