In many ways one of the most remarkable demonologies is that presented in the Avesta (q.v.), the sacred book of the Mazdean religion of Zoroaster. In this ancient religion, which unlike that of the Assyrians, still exists in the Parsee community, the war between light and darkness, good and evil comes into greater prominence. Over against the good God, Ahura Mazda, with his hierarchy of holy spirits, there is arrayed the dark kingdom of demons, or daevas, under Anro Mainyus (Ahriman), the cruel Evil Spirit, the Demon of Demons (Daevanam Daeva), who is ever warring against Ahura Mazda and his faithful servants such as Zoroaster.

It may be remarked that the name of Daeva is an instance of that change from a good to a bad sense which is seen in the case of the Greek word daimon. For the original meaning of the word is "shining one", and it comes from a primitive Aryan root div, which is likewise the source of the Greek Zeus and the Latin deus. But while these words, like the Sanskrit deva, retain the good meaning, daeva has come to mean "an evil spirit". There is at least a coincidence, if no deeper significance, in the fact that, while the word in its original sense was synonymous with Lucifer, it has now come to mean much the same as devil.
There is also a curious coincidence in the similarity in sound between daeva, the modern Persian dev, and the word devil. Looking at the likeness both in sound and in significance, one would be tempted to say that they must have a common origin, but for the fact that we know with certainty that the word devil comes from diabolus (diabolos—diaballein) and can have no connection with the Persian or Sanskrit root.

Although there are marked differences between the demons of the Avesta and the devil in Scripture and Christian theology (for Christian doctrine is free from the dualism of the Mazdean system), the essential struggle between good and evil is still the same in both cases. And the pictures of the holiness and fidelity of Zoroaster when he is assailed by the temptations and persecutions of Anro Mainyus and his demons may well recall the trials of saints under the assaults of Satan or suggest some faint analogy with the great scene of the temptation of Christ in the wilderness. Fortunately for English readers, a portion of the Vendidad (fargard xix), which contains the temptation of Zoroaster, has been admirably rendered in a doctrinal paraphrase in Dr. Casartelli's "Leaves from my Eastern Garden".

The important part played by the demons in the Mazdean system may be seen from the title of the Vendidad, which is the largest and most complete part of the Avesta, so much so that when the sacred book is written or printed without the commentaries it is generally known as Vendidad Sade which means something that is "given against the demons” - vidaevodata, i.e. contra daimones datus or antidaemoniacus.

Assyrian and Akkadian Demonology

Iranian Demonology

Jewish Demonology

Early Christian Demonology

Medieval to Modern Demonology

The Book of Enoch

The Nephilim