Exallion
Mark saying he's a blood demon would get him out of so many situations where he's hated for being a demon even if they don't know all he has to say is that it was a race of spirits and demons co-existing. His moms family are the descendants of the blood demons Royal family being a race of co-existance it would have been made up of spirits and demons. Their was probably a child born of a spirit and demon in the Royal family at the time of the war, said child was sent to the human world. Grew up, lived, had children and so on. The descendants were liked by spirits hence the protection. No one knew about the demon side because they weren't negative and depressed enough for the demon side to awaken until Mark. With him being an empath feeling everyone's feeling about him being hated because he's good at his job (he said it about his blacksmithing job way back) and his family problems continued to build up then the apocalypse came and the magical beings began to get stronger which helped him awaken. Also like in this chapter where his aunt is now a spirit after her death shows how compatible they are magical beings