Mercurial Transformation is a uncommon Sorcery — Lesson card from Strixhaven: School of Mages (STX), collector number 47. Current market price: $0.34 (foil $0.27), TCGplayer market prices via Scryfall.
Until end of turn, target nonland permanent loses all abilities and becomes your choice of a blue Frog creature with base power and toughness 1/1 or a blue Octopus creature with base power and toughness 4/4.