In the oldest layers of the record, Abaddon is not a person but a place: Hebrew for 'destruction,' paired with Sheol in Job and Proverbs as the deep that lies 'naked before God.' Only in Revelation does the abyss acquire a face — 'and they had a king over them, which is the angel of the bottomless pit, whose name in the Hebrew tongue is Abaddon, but in the Greek tongue hath his name Apollyon.'
He commands the fifth trumpet's locusts — armored like horses for battle, crowned, human-faced, lion-toothed, scorpion-tailed — loosed to torment for five months. Whether Revelation intends him as a demon, a destroying angel in service, or something the text declines to resolve has occupied commentators for nineteen centuries; Bunyan's Pilgrim's Progress settled the popular verdict by making Apollyon the fiend Christian fights in the valley.
The archive files him as scripture rather than sighting: there is no folk-encounter tradition, no ward, no banishment — only the abyss, and the assurance that it has management.