What an exciting thread (finally!)

Mitra is Sanskrit for Friend, as such He started out as an avatar of Lord Visnu
 mentioned first in the Vedas. Later he seems to have risen to chief prominence
 worshipped by the Persians. Associated with the Sun but NOT the Sun, he is
 the lord of contract honor and obedience, therefore naturally worshipped by
 soldiers. He was ordered by the Sun to slay the bull of heaven and He reluct-
 antly agreed because of His obligation...the blood of that bull spilled and
 grew all earth life...then Mitra and the Sun sat down to eat.

Worship of Lord Mitra ended in Persia with the ascension of the Zoroastrians.

Hundreds of years later He was rediscovered and thrown into the Official Roman
 Pantheon (tm) for some semi-tricky reason, I forget why. But all references of
 Him ended abruptly when He was stricken from same, so apparently His worship
 was some sort of vehicle for advancement in the bureaucracy, like membership
 in the Communist Party was in the Soviet Bloc. The sociology of religion in
 ancient times is fascinating!

Oh, His B-day was 25 Dec. Ahem.

I am not sure if the mystery cult really lasted after His was booted from the
 Roman Imperial God Roster or what. It contained mostly soldiers, with 7 levels
 of initiation. They worshipped underground in caverns in pews. The bull horns
 in those temples were for scaring away or impaling evil spirits, I'm not sure
 that they had Mithraic significance or not.

I don't know that the ritual meal was of a cannibalistic nature as is the
 Christian masses. But eating deities goes way back to Old Kingdom Egypt.

Someone mentioned bullfighting. Did Mithraists sacrifice bulls? I forget. More
 likely, for a religious source, might be the shower of bull's blood enjoyed
 by the worshippers of Cybele on the Day of Blood? Cybele worship extended all
 throughout even up to France bigtime.