The Bone Pits is one of the major areas of the Underworld. It is the area immediately east of the starting point and the Labyrinth but is only accessible through an entrance in the northwestern part of the Chaos Planes.
The Bone Pits are apparently the domain of tortured spirits in the Underworld. The Reaper of the Bone Pits presides over this domain and administers punishment to those deemed by Grenth as deserving it. However, in the absence of the reaper (imprisoned by the Terrorweb Dryders), this gruesome fate seems to have engulfed more than those deserving it.
The Pits are recognizable by the large pit in the center that has three giant boney tentacles jutting out of it (perhaps a reference to Abaddon from Nightfall). The pits are inhabited by two types of necromancer foes: Dead Collectors and Dead Threshers. In addition, there are Chained Souls continuously spawning in the area. They provide the Dead Collectors with a constant supply of dead bodies for their corpse exploitation skills.