From Diablo Wiki
Uber Diablo is an Uber, one of the demons that must be slain during the Infernal Machine event, to obtain a Hellfire Ring or Hellfire Amulet. Players find Uber Diablo in the Realm of Fright, and he must be slain in order to obtain the Heart of Evil.
Uber Diablo is the newest of the Ubers, added to the Infernal Machine event in Reaper of Souls. He is not found in Diablo 3, where only the other three Ubers/Portals are required to assemble Hellfire Ring materials.
- See the Infernal Machine article for full details on the entire process.
Infernal Machine Walkthrough
Here's a quick summary of the steps in this event. See the sections below for full details about everything related to the Infernal Machine.
- Obtain a key from each Keywarden.
- Diablo 3: Keys found from the Keywardens in Acts 1-3. Infernal Machine plan and/or a random key from the Act 4 keywarden.
- Reaper of Souls: Keys from Acts 1-4 in RoS, with one key from each Keywarden.
- Craft the keys (one of each required) to create an Infernal Machine.
- Enter the Heretic's Abode in Act One Tristram town.
- Activate the Infernal Machine(s) to open a red portal to one of the Realms.
- There is only one kind of Infernal Machine in D3, and the portal opened is random. Players are advised to have 3 Infernal Machines to do all three in the same game.
- There are 4 types of Infernal Machines in Reaper of Souls, so players can open precisely the portal they wish.
- Slay the Ubers in the realm, and cross your fingers for a Demonic Organ to drop along with the other loot.
- Once you have at least 1 of each type of Demonic Organs (3 in D3, 4 in RoS) visit the Jeweler to craft them into a Hellfire Ring.
It is usually necessary to repeat the initial steps multiple times, since keys and organs do not drop every time. Even on Torment 6 they have only a 50% chance to drop. Players can farm for the keys and organs much more efficiently in multiplayer games, both for the faster killing speed and since every player in the game has a chance at each item dropping, and all characters in the game can pass through the same portal(s) to the Uber battles.
Reaper of Souls Infernal Machines
In Reaper of Souls players can make 4 different types of Infernal Machines, each of which produces a known Portal, making it possible to hunt each Demonic Organ specifically.
- Infernal Machine of Bones > Realm of Discord. Ubers: Leoric and Maghda, may drop Leoric's Regret.
- Infernal Machine of War > Realm of Turmoil. Ubers: Siegebreaker and Zoltan Kulle, may drop Idol of Terror.
- Infernal Machine of Gluttony > Realm of Chaos. Ubers: Rakanoth and Ghom, may drop Vial of Putridness.
- Infernal Machine of Evil > Realm of Fright. Ubers: Uber Diablo + summons random Ubers, may drop Heart of Evil.
Demonic Organ Drop Rates
The same odds apply to Keys from the Keywardens. These figures are identical in D3 or RoS, after D3v2 completely reworked the difficulty system. (In the previous Monster Power system it was possible to get 100% drop odds on MP10.)
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