Apiel: This nocturnal demon is one of a thousand chief dukes said to serve the infernal king Symiel.
He is part of the larger hierarchy of demons associated with the north, at least according to the Ars Theurgia. In that text, Apiel is described as possessing a very obstinate nature. He is reluctant to appear to mortals and, when he does appear, it is only at night.
SOURCE:
The Dictionary of Demons written by Michelle Belanger