The Robe of the Lich belonged to Gedna Relvel, an infamous priestess in Mournhold who was condemned for studying and practicing forbidden magics. However, she had turned herself into a lich and survived beneath the city for untold years.
In 3E 427, after Gedna Relvel's tomb was unsealed by a curious adventurer, she attempted to spread the Crimson Plague throughout the city of Mournhold by infecting rats. The lich was destroyed by the Nerevarine before the disease could spread to more than a few people and the robes were recovered from her corpse. The Nerevarine subsequently sold it to a Dunmer noblewomen by the name of Torasa Aram, who put it on display in her Museum of Artifacts in Mournhold.