The Hellfire torch is the new unique large charm added in patch 1.11.
New Unique Large Charm: Hellfire Torch
It gives the following stats:
25% chance to cast lvl 10 firestorm when stricking
+3 to random character class skills (like +3 to amazon, +3 to sorc...)
+10-20 to all atributes
+10-20 to all resistances
+8 to light radius
lvl 30 hydra 10 charges
These are the steps you take to get it.
Step 1.
You have to aquire the 3 keys, that everyone is talking about. The keys are dropped by:
Hate-Summoner
Destruction-Nithalak
Terror-Countess
Thats what they look like. When they drop they are a white item that says Key Of Terror or Key of Hate ect.
The keys DO NOT drop everytime. That would be way to easy. Supposably they have a 1/35 chance of dropping, but thats not exact. You can have more than 1 set of the keys per char, so if you want you can get 3 of each of them before you doing the next step. If you really can hold back the suspence.
Step 2.
Take the 3 keys to act 5. Put them in the cube and transmute them. That will open a red portal to Lillith.
Lillith drops
Diablos Horn.
Durial drops
Baals Eye.
Izzy drops
Mephistos Brain.
Heres what they look like:
Now guess what! You get to repeat steps 1 and 2 again and then again once more! Or if you collected 3 sets of keys before hand, you just have to repeat steps 2 twice more. Either way, its takes a while depending on your luck and how determined you are.
The best way to go about this is to get ALL 9 keys at once. Then open all 3 portals in the same game. This will gaurentee that you get each body part. Make sure you dont open the 3 portals on top of each other though. Then you won't be able to get into the other 2.
Step 3.
OK! So now that you've collected these miniscule items of the legendary brothers you're almost done. Hooray!
Take the 3 parts and go to act 5 again if your not already there. Put them in the cube and transmute them. Bam! Red Portal to Trist. Where you fight the Uber/Clones of Diablo, Baal, and Mephisto. Once you kill these ridiculously hard bosses, which all come at the
same time the last one will drop you brand new ever so coveted Hellfire torch. Now just hope you have a character that can use it!
*Updated
Heres some tips to help you get the keys faster until a new MH comes out.Look Here 
-Heres how I find the stairway down to Nithalak very easy from the waypoint. There are two places the waypoint spawns ever time. You will notice this the more you run Nith. The first way point is closer to the bottom left of the dungeon. The second is more in the middle. If your at the bottom left WP you will need to go to the NorthEast on your map and you will find the stairway there every time. If you are at the middle WP, go directly to the SouthWest corner and if its not there head to your right staying as South as possible and you should find it about half a map over. They are in those 3 places EVERY time.
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