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Leoric's Regret ( Infernal Machine of Bones).Vial of Putridness ( Infernal Machine of Gluttony).
The level 70 Hellfire Ring requires one of all four organs, the new crafting plan which costs 5,000,000 gold coins from Squirt in Act 2 and 50,000 coins to craft. The Infernal Machine plan can drop from any of the Keywardens and they all have a small chance to spawn a second key that is not particular to them.
Act 4: Gardens of Hope 2nd Tier: Nekarat - Infernal Machine of Evil. Act 3: Stonefort: Xah'Rith - Infernal Machine of War. Act 2: Dahlgur Oasis: Sokahr - Infernal Machine of Gluttony. Act 1: Fields of Misery: Odeg - Infernal Machine of Bones. As of patch 2.3 each member of a party has an independent probability of generating a machine. The machines spawn directly from the Keywardens.
No more opening 3 portals to guarantee seeing the uber you need. There are 4 different machines that can be created which correspond to the particular fights to obtain a particular organ. The Reaper of Souls update has substantially modified this process from the launch version. He also has a chance to drop any of the 3 keys.
Dropped from Nekarat the Keywarden in Act 4. If you are a melee character, it helps a lot if you lure him to one of the many stair cases in the area so he can't run away as easily. Xah'Rith is the hardest of the 3 key wardens as he teleports around a lot and have a high damage aoe attack. Xah'Rith the Keywarden is in Stonefort. Alternately make him chase you in a circle so the balls stay within his shield. Since he often (always?) appears with a slow missile shield these balls hang around sparking on him if you can stay far enough away that he isn't chasing you. He also has mortars.Īnother note here is that he is a cake walk for a demon hunter using the ball lightning attack. When he starts whirlwinding, I recommend to back up since that attack hurts a lot.
Sokahr has an electric attack and a whirlwind attack. Dahlgur oasis is quite big and he can spawn anywhere in that zone, so having multiple people helps a lot. Sokahr the Keywarden spawns in Dahlgur Oasis. He also has the jail affix and likes to kite a lot, making it difficult to engage him as a melee character. Odeg always spawns with the molten effect, and he has a big fireball spell that can do ok damage.
Odeg the Keywarden is in Fields of Misery in act 1. The updated drop rates can be found in this answer: This post has been updated for 2.0.1 to only contain the locations of the keywardens.