Chaos Sanctuary (Act 4) Farming Guide - Diablo 2
How to Reach: River of Flame (WP) > Chaos Sanctuary
Zone Level: Nightmare: 58 -- Hell: 85
Golden Chest: No
Boss/Champ Packs: 6 - 7
Hell Immunities: Fire (Doom Knight, Venom Lord & Infector of Souls), Cold (Oblivion Knight & Lord De Seis), Lightning (Storm Caster & Grand Vizier of Chaos)
Chaos Sanctuary is the home of Diablo and is one of the more difficult locations for players to farm in the game due to how many different immunities you'll encounter throughout the area on Hell difficulty. Despite the difficulty of this location it is still one of the most farmed spots in the entire game largely due to it being a level 85 area and having a lot of Champ/Boss packs as well as Super Uniques.
In level 85 areas any Boss/Champ packs that you encounter can drop items from the highest available Treasure Class which means that they can drop all of the loot possible in the game including the most rare items. For more information about Treasure Class and how it effects you check out my Diablo 2 Magic Find Guide.
There are usually 6 - 7 Champ/Boss packs inside of Chaos Sanctuary along with each of the 3 different Super Uniques that you'll fight (one Super Unique spawns when you open certain Seals). Add in Diablo and you have 11 chances per run (if you get 7 champ packs) to get an amazingly good item.
On Hell difficulty you will encounter many different immunities throughout Chaos Sanctuary for all of the different elements (Cold, Fire and Lightning). You'll find some Poison Immune mobs on Nightmare too but they are only extremely Poison Resistant on Hell (not immune).
Venom Lords and Doom Knights are immune to Fire, Storm Casters are immune to Lightning and there are Oblivion Knights which are immune to Cold. Doom Knights (melee) and Oblivion Knights (casters) are typically mixed together in the same pile with the Venom Lords and Storm Casters scattered throughout the zone in clusters.
Throughout this zone there are Seals that you'll need to activate in order to summon Diablo, opening all of the Seals and defeating the Super Uniques they summon will start the Diablo event. For more information about the Diablo fight check out my Diablo Farming Guide or Act 4 Quest 3: Terror's End.
Seal Glitch (How it works): On the sides of Chaos Sanctuary where there are two Seals each, only one will summon a Super Unique along with its minions when opened. Additionally, when all Seals are opened in Chaos Sanctuary any enemies who are still alive are immediately killed.
The Seal Glitch involves leaving one Seal closed, specifically one of the Seals that does not summon any enemies when you click on it and some enemies alive in Chaos Sanctuary as well. So long as the enemies are "loaded" in your game they will drop loot when you open the last Seal. To ensure that an enemy is "loaded" all you need to do is run by them within a few seconds (4 seconds is what most people agree is the longest time) of opening the Seal. Anyone with Teleport will be able to do this.
Note: When doing the Seal Glitch your Magic Find values don't factor in at all. Any mobs killed by the final Seal opening will drop the same loot as if they were killed with 0% Magic Find.