Nefti's Torture Chamber

Nefti's torture chamber enters the battlefield
tapped.
{t}: Add {b}{b}
{t}: Sacrifice a creature: Add {b}{b}{b}
{t},{b}{b}{b}{b}{b}: Sacrifice Nefti's torture chamber,
exile all graveyards. Create a 1/1 black spirit with flying for each creature exiled this way.