From the introduction to the paper:
"Visitors to the Vatican Museum in Rome will remember that the very first monuments, flanking the entrance to the first room in the vast gallery that leads ultimately to the Sistine Chapel, are neither saints not angels but what appear to be devils: for at each side of the entrance door, guarding it with their baleful presence, stand two most un-Christian deities with the head of a lion and gaping jaws. In both hands they bear keys, a snake encircles their bodies, and the Signs of the Zodiac are impressed on their limbs.[2] Coming face to face with these awesome figures Christians may well recall the words of St. Peter: "Be sober and watch; because your adversary, the devil, as a roaring lion, goeth about seeking whom he may devour" (i Pet. 5 . 8 ). The serpent too which envelops the body of the lion-headed deity is all too familiar, and one is tempted to identify it with that selfsame serpent which tempted our first mother, Eve, to eat of the forbidden fruit.
Yet, interesting though the Christian parallels may be, we have long known that this rather repulsive deity has nothing to do with the Christian devil, for he figured in a cult that was for long Christianity's most potent rival in the early Roman Empire. This rival religion which has left monuments throughout the length and breadth of the Roman Empire is known as Mithraism, and its roots were originally in Iran; for the god Mithra, from whom the New Persian word mehr, meaning both the "sun" and "affection" derives, was, in the Zoroastrianism of the later Achaemenian Empire, second only to the supreme Deity, Ahura Mazdah himself."
The paper concerns a discovery in the 1960's of an incomplete 600,000 word story written during WW2 by a mysterious Iranian by the name of Ali Mirdrekvandi[3], which Zaehner deduced must have been a retelling of ancient Zoroastrian myth and which, Zaehner argued, confirmed his identification of the lion-headed figure (the "Lionish god" in the story) as Ahriman, the false deity and enemy of their true god, Ahura Mazdah (Ohrmazd).
[1] - https://archive.org/details/ZaehnerZorSurvivalsFolklore
[2] - http://www.tertullian.org/rpearse/mithras/images/cimrm545.gi...