The Pit is a hellish, savage region of the Dreamtime.
Part prison, part mercenary camp, the Pit is the home of all demons. These spirits are the result of human (and similar creatures) spirits being captured while in the dreamtime, where they are brought to the Pit. There they are psychologically and physically tortured until their spirits are warped beyond all recognition, and they join the demonic ranks.
The Pit appears to be an industrial graveyard, embers constantly smoldering, with lakes of lava and toxic waste beneath a smoky black sky that rains ash. All the spirits here are warped and at least partially insane. They are prevented from escaping the Pit by the angels of Haven.