While her specific origins are unclear as she keeps her past to herself, what is known about Illyria is that was one of Satanail's earliest creations. She has no specific loyalities to her creator, preferring to fight massive battles and destroying anything that comes in her way. During the ancient times when Zangyack was first active, Illyria would be sealed away in the Underworld with most of Satanail's first Daimons. How she escaped the pit is a mystery, but since then she has kept a low key until meeting Angelus.