Baleful Mastery is a rare Instant card from Strixhaven: School of Mages Promos (PSTX), collector number 64s. Current market price: — (foil $7.93), TCGplayer market prices via Scryfall.
You may pay {1}{B} rather than pay this spell's mana cost. If the {1}{B} cost was paid, an opponent draws a card. Exile target creature or planeswalker.