Snuff Out is a common Instant card from Duel Decks Anthology: Garruk vs. Liliana (GVL), collector number 53. Current market price: $13.13, TCGplayer market prices via Scryfall.
If you control a Swamp, you may pay 4 life rather than pay this spell's mana cost. Destroy target nonblack creature. It can't be regenerated.
All Duel Decks Anthology: Garruk vs. Liliana cards and prices