Illyria, also known as Illyria the Merciless, was one of the Old Ones, the powerful pure-breed demons that ruled Earth prior to and during the rise of humankind. In 2004, she reincarnated in the body of Winifred Burkle.

Upon her predestined resurrection, Illyria immediately went about her plan to unleash her army upon humanity, but these plans were thwarted when she discovered the destruction of her army. Lost and purposeless, and driven by the memories of Fred, Illyria struggled to find her place in the new world, and ultimately joined Team Angel in their fight.