Soul Burn

Oracle Text

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.

Card Rulings

10/4/2004 Will give 1 life for each black mana used, but not more life than the amount of unprevented damage that is dealt.