Polymorph is a rare Sorcery card from Magic 2010 (M10), collector number 67. Current market price: $2.23 (foil $18.05), TCGplayer market prices via Scryfall.
Destroy target creature. It can't be regenerated. Its controller reveals cards from the top of their library until they reveal a creature card. The player puts that card onto the battlefield, then shuffles all other cards revealed this way into their library.