Mithra is older than Zarathustra — he appears in the Mitanni treaty of the fourteenth century BCE and as Mitra in the Rigveda — and the fact that he was absorbed rather than abolished tells you something about how the reform actually worked. His name is the ordinary Avestan word for contract or covenant, so the god and the institution are lexically identical, and the Mihr Yasht makes the enforcement explicit: he ruins the house, village and country of the contract-breaker, and he punishes the breaking of a contract made with a follower of the lie exactly as he punishes one made with the faithful, because what binds is the agreement rather than the counterparty. He is described with a thousand ears and ten thousand eyes, sleepless, riding ahead of the sun. Roman Mithraism, the mystery cult of the second and third centuries CE with its bull-slaying icon and grades of initiation, borrowed the name and probably little else, and conflating the two is a persistent error.