Mistform Shrieker is a uncommon Creature — Illusion card from Onslaught (ONS), collector number 96. Current market price: $0.17 (foil $0.57), TCGplayer market prices via Scryfall.
Flying {1}: This creature becomes the creature type of your choice until end of turn. Morph {3}{U}{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.)