Uldyssian's Tomb is the culmination of the Nephalem's Sacrifice uberquest. Accessible through the tenth and final stage of the Edyrem's Path when Uldyssian's memory of Diablo is defeated, it bears a resemblance to the inner part of Tal Rasha's Chamber, with Tyrael's place being taken by Uldyssian, the ultimate boss of the quest.
Uldyssian ul-Diomed. Once only a simple farmer, but the spiteful vicissitudes of Sanctuary were not satisfied. The ghosts of Seram grew restless, and Lilith, Queen of the Succubi, began to torment those of the old bloodlines. Marked by fate, Uldyssian rose to become a boy-king, rallying others like him to defend Seram and to defend all of Sanctuary. They would become his warriors of light: the Edyrem. The blood of the Nephalem was ubiquitous, but Uldyssian gathered them all. The blood of the Nephalem was mighty, and they burned a path through all who would fight for Hatred, eventually defeating Hatred's Daughter herself. But victory was only passing. Lilith, undying, lived on through the very powers she had been defeated with.
Now ruled by their Dark Edyrem King, the tortured, reality-warping visions of the warriors of light are sealed beneath Aranoch, waiting for one to release them from their eternal curse.