Angel who alligned with Satan

The whole earth has been corrupted through the works that were taught by Azazel: to him ascribe all sin. ”
— 1 Enoch 2:8

According to 1 Enoch (a book of the Apocrypha), Azazel was one of the chief Grigori, a group of fallen angels who married with female humans. This same story (without any mention of Azazel) is told in Genesis 6:2-4:

"That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose. … There were giants in the earth in those days; and also afterward, when the sons of God came in unto the daughters of men, and they bore children to them, the same became mighty men which were of old, men of renown".
1 Enoch portrays Azazel as responsible for teaching humans to make weapons and cosmetics, for which he was cast out of heaven. 1 Enoch 2:8 reads:

"And Azazel taught men to make swords and knives and shields and breastplates; and made known to them the metals of the earth and the art of working them; and bracelets and ornaments; and the use of antimony and the beautifying of the eyelids; and all kinds of costly stones and all colouring tinctures. And there arose much godlessness, and they committed fornication, and they were led astray and became corrupt in all their ways".
The corruption brought on by Azazel and the Grigori degrades the human race, and the four archangels (Michael, Gabriel, Raphael, and Uriel) “saw much blood being shed upon the earth and all lawlessness being wrought upon the earth … The souls of men made their suit, saying, "Bring our cause before the Most High; … Thou seest what Azazel hath done, who hath taught all unrighteousness on earth and revealed the eternal secrets which were in heaven, which men were striving to learn."

God sees the sin brought about by Azazel and has Raphael “bind Azazel hand and foot and cast him into the darkness: and make an opening in the desert — which is in Dudael — and cast him therein. And place upon him rough and jagged rocks, and cover him with darkness, and let him abide there forever, and cover his face that he may not see light.”

Raphael's binding of Azazel on the desert rocks of Dudael in upper Egypt appears again in the Book of Tobit, which is found in Catholic and Orthodox bibles, but not in Jewish or most Protestant bibles. In that Book (the only place in Christian bibles where Raphael appears) he accompanies the young man Tobias (Tobit) on his perilous journey to marry his cousin Sarah, whose seven previous husbands had been killed on her wedding night by the demon Asmodeus. Raphael saves Tobias from the same fate by showing him how to deal with that demon, too.

Azazel’s fate is foretold near the end of 1 Enoch 2:8, where God says, “On the day of the great judgement he shall be cast into the fire. … The whole earth has been corrupted through the works that were taught by Azazel: to him ascribe all sin."

In 3 Enoch, Azael is one of the three angels (Azza (Shemhazai) and Uzza (Ouza) are the other two) who opposed Enoch's high rank when he became the angel Metatron. Whilst they were fallen at this time they were still in Heaven, but Metatron held a dislike for them, and had them cast out. They were thenceforth known as the 'three who got the most blame' for their involvement in the fall of the angels marrying human women. It should be remembered that Azael and Shemhazai were said to be the leaders of the 200 fallen, and Uzza and Shemhazai were tutelary guardian angels of Egypt with both Shemhazai and Azael and were responsible for teaching the secrets of heaven as well. The other angels dispersed to 'every corner of the Earth'.

Another strange passage in 3 Enoch states that while the bodies of the angels would burn and die 'their souls would be with God' and the water would turn to ice 'which would be for their healing' though they did not know it. It should be remembered angels are made of fire.