The Devil, Incarnate

Deathtouch, first strike, double strike, indestructible.
This creature may only attack if your life total is 6 or below.
You may exert The Devil, Incarnate as it attacks. If you do, defending player loses 6 life, discards 6 cards and sacrifices 6 permanents, and you gain 6 life, draw 6 cards and return six cards from your graveyard to your hand.