To get farming, start a game up on the quest Prime Evil and make your way up the Crystal Colonnade to the end of the Level 1 of the Silver Spire. With that in mind, Cuckoo Gaming has put together a video guide (seen below) on how to get the most out of Nekarat in Act 4. It’s easier to farm Nekarat than it is to farm any of the other three Key Wardens and get all of the keys. One little publicized feature about the game’s new 2.0 patch is the fact that Since 1.08, Blizzard made it so Nekarat, the Key Warden in Act 4 (the one I mentioned above that drops the Infernal Machine plans) can drop all three keys-the Key of Hatred, Key of Destruction and Key of Terror, and Key of Hate. T6 difficulty will provide you with a 50% chance.

Setting it to T1 difficulty will provide you with a 25% chance of getting any of the keys to drop from the various Key Wardens. You’ll first need to play the game on Torment difficulty. The blacksmithing plans for the Infernal Machine can be found on Nekarat, the Key Warden on Act 4 (found on Level 1 of the Silver Spire).

Torment X: 90% (Double machines are not uncommon.If you want any of your characters to wear a Hellfire Ring, you’ll first need to get your hands on all three keys dropped by the various Key Wardens found in the four acts of the game to construct an Infernal Machine.

To use the machine, go to the Hermit’s hut in New Tristram (its in the north). In Reaper of Souls there are 4 different types of Infernal Machines, each of which produces a known Portal, making it possible to hunt each Demonic Organ specifically.

Diablo 2’s Pandemonium Event is the obvious inspiration for this end-game event.

Infernal Machines only drop on the Torment difficulties. Players without Reaper of Souls will only be able to make a version of the Hellfire Ring. Once a player has collected all 4 demonic organs they can be crafted into a Hellfire Ring or a Hellfire Amulet by the Jeweler. These Ubers have a chance (increasing with difficulty level) to drop a Demonic Organ. The Machines are used to open red portals to special dungeon areas where Ubers, super powered versions of certain quest bosses, must be defeated.

Now, the Keywardens drop the machines directly. Prior to patch 2.3, the Keywardens would drop keys and the player would need one of each to craft one machine.

The Infernal Machine is an end-game quest feature introduced into Diablo 3 in the v1.0.5 patch and changed in Patch 2.3.

Diablo 3 infernal machine locations