Ob Nixilis, Planeslayer

X: Put a 1/1 Red Black Imp creature token with haste onto the battlefield.
-4: Destroy target creature. Draw a card then discard a card. You gain 2 life.
-6: Ob Nixilis becomes a 6/6 Red Black demon with Flying, deathtouch and indestructable until end you next turn. Creatures you control gain haste.