Arimanius

In classic texts, in the context of Zoroastrianism, Areimanios (with variations) fairly clearly refers to the Greeks' and Romans' interpretation of the Persian Ahriman.

[2]:  226 The most extended passage in classical literature on Areimanios is in two sections of Plutarch[3] who describes him as the dark or evil side in a dualistic opposition with Oromazes (for Ohrmuzd or Ahura Mazda).

[b] The Areimanios ritual required an otherwise-unknown plant that Plutarch calls "omomi" (Haoma or Soma), which was to be pounded in a mortar and mixed with the blood of a sacrificed wolf.

But a destined time shall come when it is decreed that Areimanius, engaged in bringing on pestilence and famine, shall by these be utterly annihilated and shall disappear; and then shall the earth become a level plain, and there shall be one manner of life and one form of government for a blessed people who shall all speak one tongue.

— Plutarch[8][3]:  47 Scholar Mary Boyce asserted that the passage shows a "fairly accurate" knowledge of basic Zoroastrianism.

[4]:  314 Franz Cumont believed that Greco-Roman Mithraism had been influenced by some beliefs of ancient Mazdaism, including ethical dualism.

However, no evidence has been found in any mithraeum for the "omomi" (haoma, soma) cult[2] associated by Plutarch with the Persian Arimanios ritual.

Cooper conjectures that the lion-headed figure does not depict a god, but rather symbolically represents the spiritual state achieved in the Leo degree – Mithraism’s “adept” level.