Xellos

Xellos (ゼロス, Zerosu) (sometimes spelled Xelloss) is a fictional character and primary figure in the Slayers fantasy comedy light novel series and its manga, anime, and other adaptations. He is a powerful mazoku demon, who is both a help and a hindrance to protagonist Lina Inverse and her friends. Xellos is the single most powerful servant of Zelas Metallium, who in turn is one of the five retainers of Ruby Eye Shabranigdo, one of the Slayers series' evil deity-like beings. Because of this relationship, some consider Xellos Metallium to be his full name, but he calls himself simply "Xellos, the Mysterious Priest".