satanail

And they said to me: These are the Grigori, who with their prince Satanail rejected the Lord of light, and after them are those who are held in great darkness on the second heaven, and three of them went down on to earth from the Lord's throne, to the place Ermon, and broke through their vows on the shoulder of the hill Ermon [*1] and saw the daughters of men how good they are, and took to themselves wives, and befouled the earth with their deeds, who in all times of their age made lawlessness and mixing, and giants are born and marvellous big men and great enmity.

The devil is the evil spirit of the lower places, as a fugitive he made Sotona from the heavens as his name was Satanail, thus he became different from the angels, but his nature did not change his intelligence as far as his understanding of righteous and sinful things.