Aquamorph Entity is a common Creature — Shapeshifter card from Duel Decks: Speed vs. Cunning (DDN), collector number 54. Current market price: $0.23, TCGplayer market prices via Scryfall.
As this creature enters or is turned face up, it becomes your choice of 5/1 or 1/5. Morph {2}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)