The Demi-Fiend

+2: The Demi-Fiend deals three damage to target creature.
-X: Search your library for a creature spell with converted mana cost X or less, and put it onto the battlefield. Shuffle your library.
-10: The Demi-Fiend becomes a 10/10 creature with indestructible, protection from colors, and "this creature can't be blocked" until end of turn.