MsMcDucket....He is one of a group of angels (in fact, a leader of them with Shemihazah) who descend to earth to teach humankind divine knowledge, and to intermarry with the women of the earth. The Asael myth is very close to that of Prometheus, who taught humankind how to make fire but who was later bound forever as punishment (the Greek myths, in fact, are partially derived from the same ANE myths that 1 Enoch derives from, cf. Shemihazah whose name may reflect the name of Mount Hazzi = Cassius in Greek myth). As Narkissos pointed out, this Enochic myth was originally entirely independent of the Azazel of Leviticus, tho similarity in the names and the desert locale led to mutual assimilation of the two beings in later Jewish thought.
Narkissos are you saying that they were Nephilim spirits? The plot thickens!
The idea that the demons are the released spirits of the Nephilim can be found in different forms throughout early Jewish and Christian literature, cf. 1 Enoch 15:6-9, 19:1, 89:6, 99:7, Jubilees 7:20-28, 10:1-2, Justin Martyr, 2 Apology 5.2, Athenagorus, Plea 6.3.2, Minucius Felix, Octavian 26, Tertullian, De Idololatria 4, Lactantius, Divine Institutes 2.15, Commodianus, Instructiones 3, Pseudo-Clementines, Homily 8.10-20. Consider the last of these:
"But from their unhallowed intercourse [between human women and angels] spurious men sprang, much greater in stature than ordinary men, whom they afterwards called giants ... they were greater than men in size, inasmuch as they were sprung of angels; yet less than angels, as they were born of women... But they, on account of their bastard nature, not being pleased with purity of food, longed only after the taste of blood. Wherefore they first tasted flesh. And the men who were with them there for the first time were eager to do the like... But by the shedding of much blood, the pure air being defiled with impure vapor, and sickening those who breathed it, rendered them liable to diseases, so that thenceforth men flied prematurely. But the earth being by these means greatly defiled, these first teemed with poison-darting and deadly creatures... God wished to cast them away like an evil leaven, lest each generation from a wicked seed, being like to that before it, and equally impious, should empty the world to come of saved men. And for this purpose, having warned a certain righteous man, with his three sons, together with their wives and their children, to save themselves in an ark, He sent a deluge of water, that all being destroyed, the purified world might be handed over to him who was saved in the ark, in order to a second beginning of life. And thus it came to pass... Since, therefore, the souls of the deceased giants were greater than human souls, inasmuch as they also excelled their bodies, they, as being a new race, were called also by a new name. And to those who survived in the world a law was prescribed of God through an angel, how they should live. For being bastards in race, of the fire of angels and the blood of women, and therefore liable to desire a certain race of their own, they were anticipated by a certain righteous law. For a certain angel was sent to them by God, declaring to them His will, and saying: -- 'These things seem good to the all-seeing God, that you lord it over no man; that you trouble no one, unless any one of his own accord subject himself to you, worshipping you, and sacrificing and pouring libations, and partaking of your table, or accomplishing nothing else that they ought not...' Having charged them to this effect, the angel departed. But you are still ignorant of this law, that every one who worships demons, or sacrifices to them, or partakes with them of their table, shall become subject to them and receive all punishment from them, as being under wicked lords.... But you should know that the demons have no power over any one, unless first he be their table-companion" (Homilies, 8.15-20).
See also the Acts of Thomas, 32, in which Satan declares: "I am the one who cast the angels down from above and bound them fast in their desire for the women, so that earth-born children might be born of them and I might work my will in them," i.e. the demons who continue to work evil. Note also the evil spirits who possess swine in Matthew 8:32, who end up drowning themselves. This repeats the same fate the demons originally had as the Nephilim, who died through drowning during the Flood and whose spirits were released upon the death of their physical bodies. That is why the demons always seek new bodies to inhabit in the gospels, because they lost their original physical form (cf. Matthew 12:43).