Mazdeism is the only religion in whose symbolism the serpent never plays any but an evil part, for even in that of the Bible it sometimes wears a benign aspect, as, for instance, in the story of the brazen serpent. The reason is, that in the dualistic conception of Zoroastrianism the animal itself belonged to the impure and fatal creation of the evil principle. Thus, it was under the form of a great serpent that Angromainyus, after having tried to corrupt Heaven, leaped upon the earth; it was under this form that Mithra, god of the pure sky, fought with him; and, finally, it is under this form that he is eventually to be conquered and chained for 3000 years, and at the end of the world burned up with molten metals.[75]
In these Zoroastrian records, Angromainyus, under the form of a serpent, is the emblem of evil and personification of the wicked spirit as definitively as is the serpent of Genesis, and this in an almost equally spiritual sense. In the Vedas, on the contrary, the same myth of the conflict with the serpent has a purely naturalistic character, evidently describing an atmospheric phenomenon. The idea most frequently repeated in the ancient hymns of the Aryans of India at their primitive epoch, is that of the struggle between Indra, the god of the bright sky and the azure, and Ahi, the serpent, or Vritra, the personification of the storm-cloud that lengthens out crawling in the air. Indra overthrows Ahi, strikes him with his lightnings, and by tearing him asunder sets free the fertilizing streams that he contained. Never in the Vedas does the myth rise above this purely physical reality, never does it pass from the representation of the warring atmospherical elements to that of the moral conflict between good and evil, as it does in Mazdeism.