Mithras (sanskrit: friend) is thought by some originally to have been an Indian deity who came via Persia to the West. In the Vedas he is presented as a spirit of light, probably the god of the upper air. However, the iconography of Mithras in Iranian religion is rather different to that of Roman times, which may indicate that they simply took the name of a already existing deity and then changed what that deity was. In Zoroastrianism (the vehicle whereby he came to the West) he became the power of truth, a solider of Ahura Mazda.
David Ulansey has posited a new and influential theory about the iconography of Mithras (the only means by which scholars have guessed at his myth, as texts about him are rare) involving astrology, which can be found at: http://www.well.com/user/davidu/mithras.html
Mithras was born from a rock (suggesting the sun rising over the mountains, or that he was born from the cosmos, and giving a sense that he was greater than the cosmos) and struggled with the bull, which was Ahura Mazda's first creation. The bull became exhausted and Mithras dragged it to a cave. The bull then escaped and the Sun sent a raven to track it, while Mithras (obeying Ahura Mazda) followed it with his dog. When he found it he stabbed the bull in the throat and from the outpouring of blood sprang corn. Then the Sun yielded to Mithras and knelt before him, whereupon he (the Sun) was given a crown and had a sacramental meal with Mithras.
Zoroastrianism was a dualist religion, with a good god (Ahura Mazda) and an evil god (Ahriman), who was described as the god of this world. (See 2 Corinthians 4:4). Mithras was seen as a mediator between Ahura Mazda and man, between heaven and earth, (See 1 Tim 2:5; Hebrews 9:15, 12:24) as well as being the divine representative of Ahura Mazda on earth, the one who protected the righteous from Ahriman. Under the reformed Zoroastrianism after Zarathusra, Mithras was said to have incarnated on the earth. He was born of a virgin, human mother (see Matthew 1, Luke 1) called Anahita, and ascended into heaven (see John 20 et al) in 208BCE, 64 years after his birth. He was described as God of truth (see John 14:6), and as the 'light of the world' (see John 8:12) - he later became linked, and finally submerged with, sol invictus, the Roman god of the sun.
Mithraism was reported as a mystery religion from 67BCE (Plutarch) and was at its height in the 3rd Century CE, and one of the chief centres of its worship was Tarsus(!) It was a male-only cult (although it had fraternal relations with the Cybele cult). There were seven altars, seven steps and seven grades of initiation. The grades were called Father, Courier of the Sun, Persian, Lion, Soldier, Bridegroom and Raven. The initiations involved endurance tests and a communal meal of wine and, in Konjica, something remarkably similar to hot cross buns. During the first initiation, an initiate drank wine and ate bread which had lain in the sun, to symbolise the internalisation of the sun's essence. (see 1 Corinthians 11:20-29). Initiates were required to undergo ritual cleansing through baptism (see 1 Peter 3:21, Mark 16:16, Acts 2:38, 22:16, Romans 6:3 et al) in the blood of a bull (the taurobolium) which:
"...had become a means of obtaining a new and eternal life; the ritualistic ablutions were no longer external and material acts, but were supposed to cleanse the soul of its impurities and to restore its original innocence; the sacred repasts imparted an intimate virtue to the soul and furnished sustenance to the spiritual life."
(Franz Cumont "Les Mystères de Mithra")
When an initiate reached the grade of 'soldier' (second level), they were branded with the a cross on the forehead, as a symbol of the sun. Initiates were taught camaradiere, considering each other to be sons of the same father, and celibacy, as Mithras was celibate while on earth, combined with victory, strength and integrity - these elements made his cult very popular among the soliders. An added attraction, of course, was that Mithras would lead his followers into eternal life in the heavenly regions after death.
The greatest festival of Mithras was held on December 25th, and services were held on Sundays, when bells were rung and praises sung to Mithras. On great occassions, the initiates would participate in a sacramental meal of bread and wine while bulls were being sacrificed.
Tertullian, The Prescription Against Heretics xl
"He [Satan], too, baptizes some—that is, his own believers and faithful followers; he promises the putting away of sins by a layer [of his own]; and if my memory still serves me, Mithra there, [in the kingdom of Satan,] sets his marks on the foreheads of his soldiers; celebrates also the oblation of bread, and introduces an image of a resurrection, and before a sword wreathes a crown. What also must we say to [Satan's] limiting his chief priest to a single marriage? He, too, has his virgins; he, too, has his proficients in continence."
(Online text: Tertullian.org)
Justin Martyr Dialogue with Trypho, a Jew, lxx
"And when those who record the mysteries of Mithras say that he was begotten of a rock, and call the place where those who believe in him are initiated a cave, do I not perceive here that the utterance of Daniel, that a stone without hands was cut out of a great mountain, has been imitated by them, and that they have attempted likewise to imitate the whole of Isaiah's words?"
(Online text: Christian Classics Ethereal Library)
Justin Martyr First Apology, lxvi
"For the apostles, in the memoirs composed by them, which are called Gospels, have thus delivered unto us what was enjoined upon them; that Jesus took bread, and when He had given thanks, said, "This do ye in remembrance of Me, this is My body;" and that, after the same manner, having taken the cup and given thanks, He said, "This is My blood;" and gave it to them alone. Which the wicked devils have imitated in the mysteries of Mithras, commanding the same thing to be done. For, that bread and a cup of water are placed with certain incantations in the mystic rites of one who is being initiated, you either know or can learn."
(Online text:Christian Classics Ethereal Library)
Jerome Letter CVII: To Laeta 2
"And to pass over such old stories which to unbelievers may well seem incredible, did not your own kinsman Gracchus whose name betokens his patrician origin, when a few years back he held the prefecture of the City, overthrow, break in pieces, and shake to pieces the grotto of Mithras and all the dreadful images therein? Those I mean by which the worshippers were initiated as Raven, Bridegroom, Soldier, Lion, Perseus, Sun, Crab, and Father? Did he not, I repeat, destroy these and then, sending them before him as hostages, obtain for himself Christian baptism?"
(Online text: NewAdvent)
Firmicus Maternus The Error of the Pagan Religions (De Errore Profanium Religionum"), 5.1-2; 20.1
A Christian author, writing c350CE. A 4th Century fundy!
"The Persians and all the Magi who dwell in the confines of the Persian land give their preference to fire and think it ought to be ranked above all the other elements. So they divide fire into two potencies, relating its nature to the potency of the two sexes, and attributing the substance of fire to the image of a man and the image of a woman. The woman they represent with a triform countenance, and entwine her with snaky monsters. This they do so as not to disagree in any way with their sponsor, the devil; they want to have their goddess be sprounting all over with snakes and thus be adorned with the devil's polluted insignia. The male they worship is a cattle rustler, and his cult they relate to the potency of fire, as his prophet handed down the lore to us, saying: mysta booklopies, syndexie patros agauou ["initiate of cattle-rustling, companion by handclasp of an illustrious father"]. Him they call Mithra, and his cult they carry on in hidden caves, so that they may be forever plunged in the gloomy squalor of darkness and thus shun the grace of light resplendent and serene. O true consecration of divinity! O repulsive inventions of a barbaric code! Him whose crimes you acknowledge you think to be a god. So you who declare it proper for the cult of the Magi to be carried on by the Persian rite in these cave temples, why do you praise only this among Persian customs? If you think it worthy of the Roman name to serve the cults of the Persians, the laws of the Persians,...
"Another pagan sacrament has the key word theos ek petras ["God from a rock"]. Why do you adulterate the faith and transfer this hold and worshipful mystery to pagan doings? Different is the stone which God promised He would lay in making strong the foundations of the promised Jerusalem. What the symbol of the worshipful stone means to us is Christ. Why do you with the knavery of a thief transfer to foul superstitions the dignity of a worshipful name? Your stone is one that rain follows and the disastrous collapse of tumbling towers; but our stone, laid by the hand of God, builds up, strengthens, lifts, fortifies, and adorns the grace of the restored work with the splendor of everlasting immortality."
(Trans: Clarence A Forbes, Firmicus Maternus: The Error of the Pagan Religions, Ancient Christian Writers, New York, Paulist Press, 1970)
Mithras: David Fingrut from the University of Kansas.
The Cosmic Mystery of Mithras By David Ulansey
The Mithraeum A religious organization dedicated to the worship of Mithras
Catholic Encyclopaedia entry on Mithras
Similarities between Mithras and Christ