Kidnapped as an infant and raised a slave for her master's daughter, Elsis quickly drew the girl's attention as being smart, quick, and strong, eventually making her eligible for the arena. She was trained alongside her master's guards starting at the age of fifteen, then thrown into the arena when she was twenty. Despite the nature of her race, she had been raised with an anti-magic collar and bracers, so while she was able to grasp the basic theory of magic she had no experience, as well as living in quarters with anti-magic wards to prevent even those who escaped their chains from casting. Because of such strong suppression, she didn't gain her headwings until she was nearly forty years old. Another battle slave was able to explain to her what Cubi were, and with much effort, she was able to hide her headwings before her battles the next day. Over the course of months she practiced shapeshifting at night, fighting in the arena each day, losing her arm during this period. She began formulating a plan, and finally put it into motion, deliberately taking a near fatal blow to the neck, knowing that it would cost her master less to save her than replace her. Her plan paid off, and when she woke in the infirmary her collar had been removed. With the use of her shapeshifting she escaped from her restraints and was able to take on the appearance of another slave, making her way to the arena and killing the guards, releasing the battle slaves and leading them to their master, overpowering him. At her insistence they left him and his family alive, locking them in the arena barracks. She then released the rest of the slaves, leading everyone deep into a nearby forest, through the mountains on the other side, and into another forest. She settled there with most of the slaves, and soon families began to form, with Elsis as the unofficial leader of the "town." Other Cubi slaves taught her more about their race, and as soon as she learned how she began tormenting the dreams of her former master, something she kept up for the rest of his life. As the decades went on, Elsis had more children, soon establishing the dominant clan among the Cubi in the settlement, eventually becoming a powerful enough bloodline to reign over the Mythos breeds, and finally the entire settlement consisted of Elsis's clan. Her ascension came through the willing surrender of her clan's souls to her over centuries, and happened around the same time as her clan's complete dominance of the town.

At the time of her death, she was sheltering multiple other Cubi clans in her territory, and her unintentional heir was a succubus named Anaiya who took the title of Elsis for herself on ascension. Anaiya's ascension was brought on by the method Elsis used to disperse her power to the survivors of the attack that took her clan down, as it essentially turned Anaiya into the same type of power conduit as a true Clan Leader.