Drain Life | Magic: The Gathering
Formats Drain Life is Legal in
Official Oracle Text for Drain Life
Drain Life deals X damage to target creature or player. You gain life equal to the damage dealt, but not more life than the player's life total before Drain Life dealt damage or the creature's toughness.
Official Rulings for Drain Life
10/4/2004 : You may gain up to the total toughness of the creature even if it was already damaged.