Diablo Wiki

The Worldstone Keep Level 2
Act Act V
Quests Eve of Destruction
Monsters Frenzied Ice Spawn,
Greater Hell Spawn
Uniques on Normal Hell Lord,
Greater Hell Spawn

(Uniques are disabled on Normal)

Monsters - Nightmare,Hell Frenzied Ice Spawn
Guest Monsters Greater Hell Spawn,
Soul Killer,
Serpent Magus,
Horror Mage P,
Horadrim Ancient,
Steel Scarab,
Black Soul
Uniques and Champions Quantity 2-3 (Nightmare)
6-8 (Hell)
Adjacent Zones Worldstone Keep Level 1, Worldstone Keep Level 3
Area Level Normal 40
Area Level Nightmare 65
Area Level Hell 85
Waypoint Yes

The Worldstone Keep is the last building, protected by three Ancients, where Baal is. The entrance is sealed until those Ancients are defeated.

The most fearsome Oblivion Knights can be found there at Nightmare Difficulty and Hell Difficulty.

It is also one of the area level 85 zones on Hell added in patch 1.10, meaning the monsters there have a chance of dropping high level items compared to other places - however, due to the Willowisps and Oblivion Knights it might not be the easiest place to do Magic Find runs.