Over twenty years after these events, the fortress was occupied by Malthael’s Reaper forces, killing its former inhabitants to scavenge D2 Items. The fortress was reshaped to reflect Malthael’s will and massive soul constructs were built that powered the central core. In order to defeat Malthael, the Nephalem had to direct this soul power into him/her, in order to enter the same state as Malthael and make him vulnerable to their attacks. Malthael was ultimately defeated.
History of the Fortress for D2 Items
The Great Conflict was waged over the Worldstone, which lay in the heart of Pandemonium. During the war, the archangel Tyrael ordered that a bastion be built around the object, the Worldstone itself kept within a guarded chamber. This stronghold came to be known as the Pandemonium Fortress.
Over the course of the conflict, the fortress changed hands many times between angels and demons and as a result, took on structural and metaphysical traits from both the High Heavens and Burning Hells. Other outposts were maintained around the fortress as well. However, this state of affairs came to an end when Inarius and his renegades were able to steal the stone from the fortress, beginning a series of events that would lead to the creation of Sanctuary and its inhabitants, humanity.
It appears that even after agreeing to leave Sanctuary be, the powers of Heaven and Hell continued to war over the fortress for a time. The blood of thousands of champions of the Light was spent in these battles, many of such champions being mortal. However, as it no longer contained the Worldstone, the interest of Heaven and Hell in the fortress had severely waned.
Returning to Hell to Get Diablo 2 Items
By the time of the Prime Evils’ intended return to Hell, the Pandemonium Fortress was occupied by the forces of Heaven, and was their last bastion before the Gates of Hell to gather more Diablo 2 Items. However, by this point, it had effectively been abandoned. Diablo, having passed through the Infernal Gate passed through the fortress before entering Hell. Still, it was from the fortress that a group of heroes, at the behest of Deckard Cain and Tyrael himself, were able to venture into Hell and thwart Diablo’s plan.