He has a little more life though, and summons Ghoul Lords and Ghosts, which are both Physical Immune. Гњber Baal is pretty much the same as Hell difficulty Baal. He has tons of life and summons Pit Lords which are immune to everything but Physical damage. Pandemonium Diablo is a 'tank' for Гњber Baal. Гњber Mephisto has a Conviction Aura, which causes -65% to all of the player's/players' resistances, and summons Skeleton Mages and Archers everywhere, which can be a challenging task. The main objective for the player(s) upon reaching Гњber Tristram is to find and defeat Гњber Baal, Гњber Mephisto, and Pandemonium Diablo (called so since Гњber Diablo already exists in-game as part of another event). There are also varieties of Unique Monsters, Champions and their minions along with the masters of the pack, the Гњber Prime Evils themselves.

Гњber Tristram has the same base structure as the regular Tristram, but has a pack-load of hellish monsters, like the rare and powerful Balrogs. This will create the portal to Гњber Tristram. Once the player(s) has/have all of the three Major Keys, they may go back to Harrogath and transmute them in the Horadric Cube. Lilith's description ( src) Additional Information

It is only here that heroes can hope to best the Three once more, and save Sanctuary from certain destruction.' The Three amassed their forces in a ravaged outpost within the mortal realm - Гњber Tristram. Rage and a deep yearning for revenge boiled within the eyes of the Lord of Terror, and together he and Lilith resurrected the two remaining Prime Evils as well as Duriel and Izual, two of their strongest agents.Дiablo announced his grand plan - the Three were finally strong enough to spread Pandemonium throughout Sanctuary. This ritual, long thought to be impossible by the most powerful mortal wizards, allowed Lilith to link with Diablo across realms, strengthening him until he was finally able to once again reincarnate himself in the mortal plane. She masterminded the revival of Diablo by manifesting herself in the mortal realm and performing a ritual of Dark Summoning. 'After her legions of Succubi and strongest daughter Andariel were killed by mortals who successfully defended the Worldstone, Lilith, the Queen of the Succubi and matron of all demons, swore to personally intervene. In this version of the town, high leveled players must take up the task of defeating the combined forces of the all-powerful Prime Evils: Гњber Baal, Гњber Mephisto, and Pandemonium Diablo.Д«ackground Note: considering that the Pandemonium Event is a only quest and is not available in the Single player or even open games, it is generally not considered to be a part of official lore. It is an exact copy of the destroyed Tristram that is found in Act I. Гњber Tristram is a special zone that can be accessed only during the Pandemonium Event. Гњber Baal, Гњber Mephisto, Pandemonium Diablo Returned, Horror Archer, Bone Mage (Cold), Burning Dead Mage (Fire), Horror Mage (Lightning), Horror Mage (Poison), Specter, Dark Lord, Pit Lord (All are spawned by the Гњbers)

Path of diablo single player