Orobas, Doombringer

Pact 6+X (You must sacrifice X demon creatures before you may cast this spell.) where X is the number of demons you control -6.
{b}{b}{b}{b}{b}{b}, {t}- You may add a black 3/3 demon token on the battlefield under your control. If you don't add one +1/+1 counter on each demon you control, including Orobas, Doombringer.
At the end of your turn, if you attacked and you control at least 6 demons who's total attack power and toughness is at least 6, you win the game.