Soul Burn is a common Sorcery card from Coldsnap Theme Decks (CST), collector number 161. Current market price: $0.30, TCGplayer market prices via Scryfall.
Spend only black and/or red mana on X. Soul Burn deals X damage to any target. You gain life equal to the damage dealt, but not more than the amount of {B} spent on X, the player's life total before the damage was dealt, the planeswalker's loyalty before the damage was dealt, or the creature's toughness.