Origen

“ But, according to our belief, it is true of all demons, that they were not demons originally, but they became so in departing from the true way; so that the name “demons” is given to those beings who have fallen away from God. Accordingly, those who worship God must not serve demons. We may also learn the true nature of demons if we consider the practice of those who call upon them by charms to prevent certain things, or for many other purposes. For this is the method they adopt, in order by means of incantations and magical arts to invoke the demons, and induce them to further their wishes. ”

“ And it is not we alone who speak of wicked demons, but almost all who acknowledge the existence of demons. Thus, then, it is not true that all observe the law of the Most High; for all who fall away from the divine law, whether through heedlessness, or through depravity and vice, or through ignorance of what is right, all such do not keep the law of God, but, to use a new phrase which we find in Scripture, “the law of sin.” I say, then, that in the opinion of most of those who believe in the existence of demons, some of them are wicked ”