Sorin, the Nightbringer

+3: Until end of turn, Sorin, the Nightbringer becomes a 5/5 Demon creature with flying and lifelink that's still a planeswalker.
-3: Exile target creature or planeswalker. You gain life equal to its converted mana cost.
-15: Sorin, the Nightbringer deals 20 damage to target creature or player and you gain 20 life.