Maelstrom Muse is a uncommon Creature — Djinn Wizard card from Strixhaven: School of Mages (STX), collector number 202. Current market price: $0.17 (foil $0.29), TCGplayer market prices via Scryfall.
Flying Whenever this creature attacks, the next instant or sorcery spell you cast this turn costs {X} less to cast, where X is this creature's power as this ability resolves.