Lady Azeroth
Originally a Low-ranking succubus, she was chosen by Leviticus as one of his personal pleasure slaves, where she experienced all manner of cruel and inhumane treatment. When Leviticus was imprisoned in ice for plotting to overthrow Amodeus, she was claimed as a spoil of war, and treated with equal amounts of sadism by the lord of the 9 hells.
In the 16th century, when Victor Stein set about the events of The Fall, and successfully claimed control of the Infernal plane to be used as his personal laboratory, She was recognized for here intelligence and knowledge of demonics and nethermancy - both subjects Stein was keen to expand the knowledge of. She was given directorship of the 3rd research division of hes newly formed Victorian institute - one of the only native denizens of the infernal plane to receive such a distinction.
She was in fact, promoted to the position over Adam Virus, the power-hungry son of the Arch-Inquisitor Stein had presumably worked under before his betrayal of the church. Virus held a strong animosity towards her for this, but also a sadistic attraction, which would later be his downfall. Virus and Azeroth worked together closely on the Umbraviralis project, until Virus orchestrated a containment breach, attempting to blame Azeroth, and gain directorship over her department in doing so. Stein saw through the ruse, and instead demoted Virus further of the catastrophe, causing even further resentment.
When Virus later turned against Stein and the Treatise Divinitas during the events of the 1862 world's fair, It was Azeroth, leveraging Virus' infatuation with her, who was able to help infiltrate his newly claimed divine realm and kill him, thus beginning what would later become recognized as an ongoing cycle of death and resurrection for Virus.
Less than a Year later, when the Princess of dreams was corrupted by Nemesis, giving birth to the first hollowers, Azeroth Sacrificed herself at the site of the Notre Dame cathedral, protecting the denizens of Paris from the worst of the incursion. It was this act of selflessness that seems to have inspired her still unexplained resurrection as a Divinity a year later - after which she left the Victorian Institute to form her own Divine realm, claiming the domains of shadow, Mercy, Perversions, and Repentance.
Due to her extensive time spent in sexual slavery to the sadistic lords of the nine, Azeroth developed a masochistic streak that she would carry with her even into her Divinity, and was known to seek out dangerous and horrific lovers to sate these needs. Like many other Divinities of her time, she was well known to walk the streets and engage directly with mortals, and worked for untold centuries attempting to undue the harm caused by the Umbraviralis plague.
She purportedly disappeared with the other Deities of Atheros several hundred centuries ago, and while most Information about her (including much of the above) has been lost to time, she is still worshiped in small cults on the surface, and is a popular figure of reverence within some parts of the dungeon - especially the succubus dens. Some suggest that she may even have been an early avatar of The Mistress