Bone Pits, abbreviated as "pits", is the name of an area in The Underworld.
When this quest is taken from the Pits Reaper, a group of 3 yellow dryders will spawn in the "centre" area. After 5 seconds, either a skele or a white dryder will also spawn in that area. Another 5 seconds later, a skele or white dryder will spawn in the "back side" area. Every 5 seconds, a new foe will spawn, alternating between centre and back side, until 3 such foes have spawned at each point. Whether each spawn is a skele or a white dryder is completely random, with no connection to what the previous spawn was. 30 seconds after taking the quest (as the last skele or white spawns on back side), a second group of 3 yellow dryders will spawn in the centre, and a third will spawn after another minute, this time slightly closer to the bridge. All of these enemies will head towards the Reaper, but will stop to fight anyone they encounter.
Meanwhile, allied Tortured Spirits will spawn in the area between centre and back side, starting with one the moment the quest is taken, and followed by one more every 10 seconds until there are 4. Once they've all spawned, they will gradually start walking slowly towards the Reaper, but will rush to attack anything they aggro. Once they leave aggro, they will walk slowly back to the path to the Reaper. If any of these Tortured Spirits dies, the party will be defeated, but once they reach the Reaper, they will become invulnerable and disappear from the party list. When all 4 reach the Reaper, the quest will complete, although the Tortured Spirits will stop moving and not complete the quest while nobody is in compass range.
Pits is entered from the north-east of Planes, with a long, narrow corridor leading a large area of winding cliffs. The path leads under a bridge and up a slope, around to cross the bridge, entering the "centre" area of Pits. To the north-east is the "back side" area, and to the north-west is a hill leading up to the Reaper monument.