"One day every soldier in the empire has to shower in the blood of your sacrificial bull. The next they don't even remember your birthday." --Neil Gaiman, American Gods*
I have to add a disclaimer to this post. Mithraism is NOT a single mythological tale, but a full mythic cycle which was eventually adopted and adapted by the soldiers of the Roman Legions into a belief system which (from my perspective) rivaled early Christianity. And so, while I'm fascinated by Mithra and his rituals and myth, this is not an in-depth study of an entire religion. If it was, I'm pretty sure most of you would run like hell, and on top of that I eventually need to sleep. Also, I am not an archaeologist, and I KNOW I have a few friends who might be more learned on this topic than I. Please please correct me if I'm wrong: there's a lot of detail I have to leave out to keep this a under-10,000 word post. Or feel free to add in comments!
Mithra seems to have originated as a god in the Zoroastrian pantheon of ancient Persia (generally around Iran/Iraq and part of Turkey today). Again, Zoroastrianism is a full religious cycle, and deserves its own series of posts. The key concepts, however, are that where Abrahamic religions say God is the creator and sovereign of all (including evil, which God created), Zoroastrian belief allows for a good and evil rivalry. Oromasdes and Ahriman (that'd be Good and Evil, only with unpronounceable names) are both looking for souls of man. Ahriman is willing to send demons and evil spirits to tempt or force man to his side. Mankind needs some help down here, and Mithra is sent as the savior hero-god.
As a hero-god, he has two main incidents in the Persian cycle. In the first, Mithra battles the Sun and wins, becoming "Helios Mithras"...the Sun God. That's a little weird because Helios (the actual Sun) is still around and just really good friends with Mithra in many of the myths.
One of the joys and frustrations of mythology, people, is that sometimes it's just the earliest example of the telephone game.
The key here is that Mithra is now fully a God of Light, which plants him pretty firmly as "God's Savior of Many on Earth." Yes, this sounds familiar. I'm getting to that.
The other major theme in Mithraic beliefs is his slaying of the heavenly bull. Mithra is reluctant to do so, but slays the bull in a cave on command/request of another God. The body of the dying bull becomes all the wholesome plants and animals on Earth, and his soul retreats to the heavens as reward. Mithra guards this new abundant land and acts as mediator between God and Man, until it is determined he is no longer needed on Earth and he returns to Heaven as well.
Mithraic beliefs seem to have included the dualism of good and evil (of course) as well as a philosophy of abstinence (that'd be abstinence in all things not absolutely necessary, not just sexually), loyalty, duty, and discipline. Also, no women allowed** (I wonder if they had that inscribed on the temple doors).
Therefore, it's pretty easy to see why the Roman soldiers would've grabbed that cult and made it their own. After all, Rome absolutely excelled at figuring out the best parts of a different civilization and incorporating it into Roman society, and the Mithraic cycle of stories exemplified all the ideal soldier attributes. And remember, between the wars that are written of to exalt or ridicule an Emperor's reign, there were also years of peaceful trading going on along all the borders. This cult would've found an easy home with soldiers' outposts and traveled quickly through the ranks.
However it happened, from the 1st to 4th Centuries CE Mithraism was THE belief system of the Roman Army. And as they did so very well with other cultures, Rome took Mithra and made it her own. The name was Latinized to Mithras. The central mythology adjusted slightly to focus on Mithras as the Sun God in eternal battle with Evil. The Sacrifice of the Bull to create the world and cleanse man of sin became the central myth.
Roman Mithraic Mysteries included elaborate initiation rituals to seven degrees of membership. There are references to a "complete guide" account of Mithraism, but the book itself has never been found. I think that's a serious bummer: one of the initiation rituals rumored to be enacted was the sacrifice of a bull over a pit, in which the initiate was essentially showered in the bull's blood at it's death. I can't find confirmation on the accuracy of this rite, but if it did happen I suppose that explains the serious attention regarding post-initiation ritual baths. I have to say, given the number of soldiers who were active participants, that sort of rite (were it true) may have been a high-echelon member initiation only...meaning only the seventh level members. Or I'm underestimating how many bulls the Legions had available for sacrifice, which is also completely possible.
There isn't a lot of direct written evidence of the rituals themselves: after all, to some extent it was a secret cult. However, archaeologists have found a ridiculous number of artifacts all over the empire. Mithraeums (underground cave temples dedicated to Mithras) have been found pretty much wherever Legions were stationed. Multiple bas-relief examples and sculptures detailing the central Bull sacrifice mythology can be viewed in museums today (or, Google, since that's easier and less expensive than traveling to the Louvre). From what I can tell, it seems wherever soldiers were stationed, Mithras hung out as well.
So what happened in the 4th Century to end Mithras' status?
Constantine. The century began with Constantine's rule, and over the course of a few decades Constantine made Christianity the official religion of the Empire. This spelled the beginning of the end of Mithras in Rome. Of course, nothing is overnight: it took quite a while before everyone in the Empire was converted (and even longer for those on the fringes). I did find some historians' theories that Theodosius' (379-390 CE) anti-paganism decrees were directly in response to stubborn pockets of Mithraism.
And true to Roman form, many of the most importantly held beliefs of the old religion were just incorporated into the new one. There are conspiracy theories of "heretics" worshiping Mithras in secret even today (which make for great novels, by the way).
After all, when Christianity subsumed Mithraism in Europe, where were many churches built? Over Mithraeums.
Mithras was God of Light and Savior of Mankind, the intermediary to God on behalf of Mankind...
Mithras' birthday? December 25th.
Of course I write that as a provocation, mostly because in researching Mithra/Mithras I included the Catholic Encyclopedia as one of my sources. It's an utterly fascinating read: all the similarities in feast rituals, savior iconography, and even ritual days are dismissed with total disdain by the Church as "evil copies" of good Christian traditions. There is an underlying tone of protest that's really interesting: is it possible there are pockets of Mithraic believers existing in the shadows today?
I suppose since I wander this planet with a vagina instead of a penis, I'll never know. I'm cool with that...bull-blood-bathing seems...well, it just sounds sticky and sort of gross. And who wants to clean the bathroom after THAT post-ritual-shower?
*If you haven't read this book and you like mythology even a little, READ IT NOW.
**It would be easy to say from a modern perspective that Mithraism is an anti-woman, patriarchal cult. However, it's vital to remember that monotheism is a relatively recent invention in human history: the Zoroastrian pantheon included multiple deities for multiple worshipers, including women's mysteries.