Illyria

Illyria is a fictional character featured in the Buffy the Vampire Slayer and Angel television franchises. Played by actress Amy Acker, she first appeared in episode 15 of season 5 of Angel entitled "A Hole in the World".

Overview
Illyria was an elder being of godlike power from another dimension who was brought to the Earth realm where she took possession of human scientist Winifred "Fred" Burkle. Displacing Fred's essence effectively killed her and Illyria took full command over the woman's body. This greatly tormented Fred's companion, Wesley Wyndam-Pryce, who harbored deep resentment towards Illyria. Wesley realized that some of Fred's memories were locked inside of Illyria's mind and he began mentoring her, desperately hoping to bring Fred back. Despite her seeming lack of compassion, Illyria joined Wesley's comrades "Team Angel", and grew to appreciate Wesley as a tutor. When Wesley was killed during the Earthly invasion of the demonic forces of the Cult of the Black Thorn, Illyria felt great rage and used what abilities she still maintained to get revenge against them. Even when Los Angeles fell to the demonic hordes, Illyria continued to fight alongside Angel, Spike and Charles Gunn.