Actually that is not correct. It was around long before Christianity, even if you don't trace it back to the ancient East .
All of the archaeology for Mithras dates from 100 AD or later; and the archaeology is our best source for the cult.
All of the literary sources date from 80 AD or later. Plutarch, writing around 100 AD, says that the Cilician pirates of 68 BC worshipped Mithras. But since he is writing 168 years later, scholars tend to suspect that he got confused with Zoroastrian Mithra, who was worshipped in that area and time period in Asia Minor. After all, Mithras claimed to be the Persian god. It is the archaeology -- mainly Latin, not even Greek -- that reveals that the cult must in fact be a Roman invention.
The devil led the heathen to anticipate Christ with respect to several things, as the mysteries of the Eucharistetc. "And this very solemnity (says St. Justin the evil spirit introduced into the mysteries of Mithra." (Reeves, Justin, p. 86)
This is a strange 'quote'. Here's what Justin says (1st Apology, ch. 66):
'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.'
"Therefore some spirit or other contrived the COUNTERFEIT that His image should be bought for blood, because he knew that the human race WAS AT SOME TIME to be redeemed by the precious blood. For evil spirits counterfeit certain shadows of honor to themselves, that they may deceive those who follow Christ. Augustine
Obviously the church fathers knew Mithras was before Christianity.
Not from this.
The ancient historian Plutarch mentioned Mithraism in connection with the pirates of Cilicia in Asia Minor encountering the Roman general Pompey in 67 BC.
True: see above. But there is no archaeology in Cilicia for Mithras earlier than the imperial period, so clearly there is a problem with Plutarch's testimony.
Tertullian Praescr, ch 40 - says that the followers of Mithra practiced baptism by water, and made a sign on the forehead of the baptized person.
The name "Mithras" in this passage may be spurious, since the passage makes more sense if it is omitted. Ritual washings were common in antiquity, and nothing may be inferred from them.
He appears to have lived an incarnate life on earth, and in some unknown manner to have suffered death for the good of mankind, an image symbolizing his resurrection being employed in his ceremonies. Tertullian, Praescr, ch. 40.
*
This is not a quotation from Tertullian, who actually says:
"The question will arise, By whom is to be interpreted the sense of the passages which make for heresies? By the devil, of course, to whom pertain those wiles which pervert the truth, and who, by the mystic rites of his idols, vies even with the essential portions of the sacraments of God. He, 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, Mithras 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."
Mithras was a god, not a man, and was not "incarnate" and did not "die".
You can obtain all the literary and quite a lot of archaeological sources from here:
The Roman cult of Mithras
All the best,
Roger Pearse
If you don't, it's okay too.
