Necros, Demon Commander

-6: Put a +1/+1 and Deathtouch counter on each black creature you control, then proliferate twice. Put 8 loyalty counters on Necros.
-8: Proliferate three times, then create a black 8/8 Demon creature token with Deathtouch under your control. Put 12 loyalty counters on Necros.
-12: Until end of turn all cards in play are black instead of their original colors. Take control of all black cards in play and lose 12 Life.