Baleful Mastery is a rare Instant card from Strixhaven: School of Mages Promos (PSTX), collector number 64p. Current market price: $2.03 (foil $3.27), 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.