Haj Uxith (translating to "Hidden Nest" in Jel) is an Argonian city found with the depths of Coldharbour, a plane of Oblivion. Haj Uxith comes from a time in Argonian civilization that came before the events known as Duskfall. In order to escape it, the Hist had made a pact with Molag Bal, which took the settlement into his realm, where the Hist would be harvested by the Daedra. A motto that the Argonians of Haj Uxith follow is to preserve the culture that their Hist attempted to keep safe.
Haj Uxith is a city whose roots harken back to the ancient history of the Saxhleel people, when they were a prospering civilization. But what changed them forever was an event known as Duskfall, which brought about many shifts in the Saxhleel civilization. While most of Argonia succumbed to change, the Hist Tree at Haj Uxith stood firm and fought against the river's current. The Hist sought to preserve its people's culture; to remain in the days of the Stone Nests. It was then that Molag Bal, the Daedric Prince of Domination, approached the Hist Tree with a proposition. The Prince offered the Argonians of Haj Uxith a safe haven in Coldharbour, where their culture could be preserved and free of Duskfall's influence. In exchange, the Hist would allow Molag Bal's minions to extract its sap. The Hist agreed, and Haj Uxith was taken into an isolated valley in the Shrouded Plain of Coldharbour, where it would remain ever since. Following their absorption into Coldharbour, Molag Bal's minions would constantly come into Haj Uxith and extract the Hist Sap from the city's Hist Tree. The residents of Haj Uxith were not permitted to enter the sap vat chamber. The Dremora had placed a vampiric crystal on the Hist Tree, which poisoned it, thus weakening it, to aggressively harvest the sap. This caused the Hist Tree to experience great pain.
During the Interregnum in 2E 582, Vanus Galerion, alongside both the Fighters Guild, and the Mages Guild, had orchestrated an assault onto Coldharbour. The various people that traveled to Coldharbour had spread across the oblivion plane, only to gather at the Hollow City. At the time, two factions in Haj Uxith were conflicting with one another on the subject of the Hist's future. The warriors of Haj Uxith wanted to keep their Hist Tree alive, albeit in torment, while the scholars of Haj Uxith want it to rest in peace. Treeminder Xohaneel had asked for the help of the Soulless One, who was a part of Galerion's invasion force. It is unknown what side the hero chose, but the situation at Haj Uxith was dealt with regardless. Those that the Soulless One had sided with would join them in the invasion against the Endless Stair.