Diablo (Act 4) Farming Guide - Diablo 2
How to Reach: River of Flame (WP) > Chaos Sanctuary
Zone Level: Nightmare: 37 -- Hell: 85
Golden Chest: Yes
Boss/Champ Packs: 6 - 7 in Chaos Sanctuary
Hell Immunities: Fire (Doom Knight, Venom Lord & Infector of Souls), Cold (Oblivion Knight & Lord De Seis), Lightning (Storm Caster & Grand Vizier of Chaos)
This is my farming guide for Diablo, the original final boss in Diablo 2 before Lord of Destruction was added. Diablo along with Chaos Sanctuary runs are one of the two most commonly run endgame farming routes in the game rivaled only by Baal runs. If you're looking for the farming guide for Chaos Sanctuary instead then follow the link provided; this page will strictly contain information about Diablo himself.
Despite being the final boss of the original game, Diablo can only drop up to Treasure Class 84. For this reason Diablo can not drop any of the TC 87 items like Griffon's Eye Diadem, Crown of Ages, Tyrael's Might, Mang Song's Lesson, Windforce and Death Cleaver to name a few. The ironic part is the Champ/Boss packs in Chaos Sanctuary around Diablo can drop these items.
You can begin the fight with Diablo by opening all of the Seals in the Chaos Sanctuary and defeating the Super Uniques along with all of the enemies summoned when you open them. If for some reason you have done all of these steps and Diablo hasn't spawned, you probably missed one of the Grand Vizier of Chaos' minions (the flying specter things).
They can fly through the walls and out over the lava which can easily lead to someone not noticing and skipping them. A screenshot of this boss and these enemies is shown above at the top of the page.
Diablo is one of the toughest fights in the game and definitely the toughest boss you've faced up until now. My recommendation is to go to town before you fight him and fill up on Healing Potions as well as Mana Potions. Put some in your inventory too or drop them in a convenient spot in Chaos Sanctuary if you're not good at using them out of your inventory quickly. When you pick them up, they'll automatically be added to your Potion Belt.
I'd also recommend you stack Lightning and Fire resist if you're struggling as they'll make this fight a whole lot easier. Diablo's primary damaging ability is Lightning and Fire is his second most commonly used element. Below I have put together a list of all his abilities so you know everything he can throw at you.
Another tip that comes to mind is don't forget that Rejuvenation Potions heal you instantly not over time. You can also drag and drop Potions over top of your Mercenary's portrait to use them on him. This can help you save your Mercenary in a pinch.
Charge: Diablo will sprint quickly across the floor on all fours like an animal.
Cold Touch: A regular melee attack with a chilling effect.
Bone Prison: Diablo will cast this around Town Portals that are too close to him.
Firestorm: Similar to Fire Wall but instead of one straight line it is many erratic lines.
Fire Nova: A ring of fire shoots out from Diablo.
Fire Wall: Same as the Sorceress skill of the same name.
Red Lightning Hose: Diablo fires a red beam out in front of him and will slowly follow the character with it. This is his most damaging ability and the main one to watch out for. Deals both Physical and Lightning damage.
Melee Character Advice: Diablo will be much harder for you than ranged. You need to watch very closely for the Red Lightning Hose that Diablo does and avoid it. For the most part you can stand in his other abilities and take his attacks without much concern but the Lightning Hose will kill you in a second if you are not careful.
Ranged Character Advice: Use the terrain around where Diablo spawns to your advantage. Try to keep distance from him and keep hitting him with your most powerful ranged attacks. If possible try to attack Diablo while he is off screen for the safest strategy. While doing this keep an eye out for Bone Prison you which you'll need to destroy as quickly as possible so you can keep moving. Diablo will use this one you when you get too far away. Avoid his Red Lightning Hose or you'll most likely die.
A big tip that I can give to you is on Nightmare and Hell you can actually avoid the Lightning Hose ability by standing close to Diablo. On Nightmare you have to be right up in Diablo's face in order to avoid it but on Hell you can stand relatively close to Diablo and avoid it easily.
The way this ability works is on each difficulty there is a bigger gap in front of Diablo and where the Lightning Hose begins. On Normal, usually the Lightning Hose comes right out of Diablo's model. That is to say it's attached to him when he fires it. On Nightmare there is a small gap in front of him and where the attack begins. On Hell that gap is noticeably larger.
As Ranged you'll want to do your best to keep Diablo off screen while attacking him.