Demon's Efficacy

Emerge {7}{b}(You may cast this spell by sacrificing a creature and paying the emerge cost reduced by that creature's converted mana cost.)
Unearth {3}{b}({3}{b}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at
the beginning of the next end step or if it would leave
the battlefield. Unearth only as a sorcery.)
When Demon's Efficacy enters the battlefield,
destroy all non-black creatures.