River, the Black Witch

Deathtouch, haste, trample
When River, the Black Witch enters the battlefield, exile cards from the top of your library until you exile a nonland card, then put that card onto the battlefield without playing it's mana cost. River, the Black Witch cannot be blocked except by artifact creatures and black creatures.
{2}{b}{t}: Sacrifice a creature, create a 3/3 black demon creature token with flying and deathtouch.
{x}{b}{b}{t}: Sacrifice an artifact, create X -X/-X tokens and place them on creatures your