Mistform Stalker is a uncommon Creature — Illusion card from Onslaught (ONS), collector number 98. Current market price: $0.12 (foil $0.53), TCGplayer market prices via Scryfall.
{1}: This creature becomes the creature type of your choice until end of turn. {2}{U}{U}: This creature gets +2/+2 and gains flying until end of turn.