Flying Demon's real name is Arthur. He is one the Twelve Demons and a disciple of Divine Demon.
He first appeared as a skeletal figure which could wither away at the slightest touch.
After Noah gave him rank 4 restorative drugs. He recovered and appeared as muscular with cold face, short black hair and green eyes. A freezing aura always enveloped him.
During the betrayal of Ravaging Demon, He and Dreaming Demon escaped into a separate dimension with the remnants of their sects. Dreaming Demon was forced into a slumber due to her divination, to keep her alive and help her awaken, he used his blood to supply energy.
He was extremely devoted to Dreaming Demon and never abandoned her during the 1000 years they spent in the Separate Dimension.