Uber Portals

Monster Level
 Location

Uber portals (not to be confused with Red Portals) are special end-game areas that house a boss in each respective portal. The main draw to running uber portals is it's the only way to get a Hellfire Torch charm, which any and every build can take advantage of. To get the torch, you must get the three different organs from each uber boss. Any given boss kill has roughly a 1/25 chance to drop an organ. Once you get the three, cube them in Harrogath for the final portal.
The uber portals are three separate areas that can be reached by gathering the key of terror (Blood Raven), the key of hate (the Summoner), and the key of destruction (Nihlathak), cubing them into a Pandemonium Fragment, and cubing the fragment while in Harrogath, fragments have 12 charges until they are used up completely. Only one portal will be spawned per charge, and each portal has an equal chance to spawn when the fragment is cubed, more than one of the same portal cannot be spawned per game.
***\*Note: never set more than one portal off in the same place, it may block you from entering one or two of them***
**Forgotten Sands**
The main element here is lightning, make sure you have plenty resistance to it due to the lightning aura the scarabs have, and the high damage the corrupt thunderess's deal. Uber Duriel (Arachonius), like normal Duriel has a constant freezing aura which cannot be blocked by Cannot be Frozen, making melee users slightly less useful. He also seems slightly more vulnerable to casters. Overall he's not too threatening and can be taken down pretty quickly.
**Furnace of Pain**
Fire and cold are the two main elements here, you'll want to have plenty of each resistance coming in here. The types of Heirophants here cast hydras that shoot piercing balls of their respective element, and can take down your minions very quickly. The Lupis Infernus hit and deal a splash explosion that deals a lot of damage, so try and keep your distance from them if you can. Uber Izual (Lucion) deals decent damage, and casts an ice nova on striking. He is resistant to elements, but is vulnerable to melee. Regardless he usually isn't much of a problem.
**Matron's Den**
You will want to stack poison and cold resistance here, as the monsters can deal large amounts of both rather quickly. The Toxic Princess's here will shoot poison balls and curse you on sight, lowering your elemental resistances. You can combat this by chugging a bunch of antidotes and thawing pots, bringing your poison and cold resistances back up respectively. Cold Hands can shoot frozen orbs, which can deal a lot of cold damage at once, even at decent resistances. Undying don't hit very hard, but are resistant to almost everything, as well as having huge regen. Lilith is usually the most problematic of the uber bosses, as she hits fairly hard and casts a wave of poison that hits you more the closer you are to it. Trying to run away from her can also be dangerous as she's ludicrously fast and surprisingly good at pathfinding.
**Notable Loot**
Any enemy in these uber portals have a small chance to drop "Diablo's Soulstone", which upon vendoring, will spawn a Diablo clone in each open Hell game. This Diablo will replace the first unique non-boss monster you find. Upon killing the Diablo clone he will drop an Annihilus small charm, this is the only way to get this charm. The Ubers themselves also have exclusive Uber Item drops. These drops are class-specific items that are usually very strange and can built around, though usually don't work well with most normal builds.