Drain Life

Oracle Text

Spend only black mana on X.

Drain Life deals X damage to any target. You gain life equal to the damage dealt, but not more life than 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 Cost reducers can be used to reduce the X part of the mana cost.
10/4/2004 You may gain up to the total toughness of the creature even if it was already damaged.