Xelloss is pure Mazoku., a Monster. He was the creation of Zelas Matellium, one of the five high ranking Mazoku created by Shabranigdo. Other Mazoku created a general and a priest; Zelas gave Xelloss the power of both. This makes him, by the end of NEXT, the fifth most powerful monster in Lina's world.

Unlike other mazoku his personality seems a more benign spirit. He introduces himself as, The Mysterious Priest or the Trickster Priest. All mazoku thrive off of the dark emotions of humans. They look on humans as pray or as a food source. Xelloss seems to prefer tease or trick people and feed off of their frustrations almost as a desert while getting his mission done.

I understand that he comes across much darker in the books than the anime. This may be closer to what we see in TRY than NEXT, where his mission allows him to be more himself, darker. Viewers have commented on how he seems different in TRY than NEXT. In NEXT his mission was to guid and protect Lina to his, rented, masters wishes. He did not like his temporary master and seems to have put his own spin onto his orders. This had the affect of strenthening Lina to an end that was not in the mazoku plans.

Zelas Matellium is Zellosses superiour and creater. She is one of the five Dark Lords created by Shabranigdo. It is by the will and plans of his superiors that he deals with humans and hat these plans are, is a secret.

Shabranigdo is the Dark Lord of Dark Lords in Lina's plane. There were four planes created by, The Lord of Nightmares. Each of these planes had a Dragon God and a Mazoku of their own.

Vaalgarv

Monsters