The Mortuum Vivicus was a powerful weapon created by the Daedric Prince Molag Bal. It had no physical form, instead appearing as a large orb of cold light. It was originally given as a gift to the Ayleid King Anumaril of Abagarlas, a Daedraphile settlement on City Isle that was dedicated to Bal. The Abagarlans planned to use the Vivicus to drain all life from the rival city of Delodiil and convert its citizens to undead servants of Molag Bal, as penance for King Cenedelin's mockery of the temple of Abagarlas. The Meridia-worshipping city of Delodiil responded by forging a powerful weapon imbued with the Prismatic Core, a powerful crystal given to them by Meridia. An elite group of warriors were then sent to Abagarlas to preemptively destroy the Vivicus. However, Bal snatched the weapon away right before it could be destroyed, returning it to his realm of Coldharbour for safekeeping.
The Vivicus would lie dormant in the Halls of Submission for several thousand years, until in 2E 582 Molag Bal began an all-out attack on Mundus during his attempted Planemeld. Using the power of the unprecedented amount of souls being sacrificed in his name, Bal hoped to return the weapon to Tamriel and "burn" the entire continent. The weapon would strip the souls of countless mortals from their hosts and create a nightmarish storm of undeath. The Fighters Guild had come under the sway of Meridia, with its guildmaster murdered and replaced by one of her worshippers, and enough money provided to dedicate the guild's entire resources towards destroying Bal's Dark Anchors and preventing the return of the Vivicus. Seeking to reveal Guildmaster Sees-All-Colors' treachery and thwart Meridia's plans, Molag Bal had his own servant, Aelif, work alongside the guildmaster and the Vestige. Aelif betrayed the guild at the last second, although she was defeated in combat by the Vestige and the Mortuum Vivicus was destroyed using the reforged Prismatic Core.