Do you know Constantine was never a Christian, eventhough it is commonly believed he was converted in a dream or his wife converted him?
Constantine as did the noble Roman class believed in Mithraism:
Mithraism
ORIGIN
The origin of the cult of Mithra dates from the time that the Hindus and Persians still formed one people, for the god Mithra occurs in the religion and the sacred books of both races, i.e. in the Vedas and in the Avesta. In Vedic hymns he is frequently mentioned and is nearly always coupled with Varuna, but beyond the bare occurrence of his name, little is known of him (Rigveda, III, 59). It is conjectured (Oldenberg, "Die "Religion des Veda," Berlin, 1894) that Mithra was the rising sun, Varuna the setting sun; or, Mithra, the sky at daytime, Varuna, the sky at night; or, the one the sun, the other the moon. In any case Mithra is a light or solar deity of some sort; but in vedic times the vague and general mention of him seems to indicate that his name was little more than a memory. In the Avesta he is much more of a living and ruling deity than in Indian piety; nevertheless, he is not only secondary to Ahura Mazda, but he does not belong to the seven Amshaspands or personified virtues which immediately surround Ahura; he is but a Yazad, a popular demigod or genius. The Avesta however gives us his position only after the Zoroastrian reformation; the inscriptions of the Achaemenidae (seventh to fourth century B.C.) assign him amuch higher place, naming him immediately after Ahura Mazda and associating him with the goddess Anaitis (Anahata), whose name sometimes precedes his own. Mithra is the god of light, Anaitis the goddess of water. Independently of the Zoroastrian reform, Mithra retained his place as foremost deity in the north-west of the Iranian highlands. After the conquest of Babylon this Persian cult came into contact with Chaldean astrology and with the national worship of Marduk. For a time the two priesthoods of Mithra and Marduk (magi and chaldaei respectively) coexisted in the capital and Mithraism borrowed much from this intercourse. This modified Mithraism traveled farther north-westward and became the State cult of Armenia. Its rulers, anxious to claim descent from the glorious kings of the past, adopted Mithradates as their royal name (so five kings of Georgia, and Eupator of the Bosporus). Mithraism then entered Asia Minor, especially Pontus and Cappadocia. Here it came into contact with the Phrygian cult of Attis and Cybele from which it adopted a number of ideas and practices, though apparently not the gross obscenities of the Phrygian worship. This Phrygian-Chaldean-Indo-Iranian religion, in which the Iranian element remained predominant, came, after Alexander's conquest, in touch with the Western World. Hellenism, however, and especially Greece itself, remained remarkably free from its influence. When finally the Romans took possession of the Kingdom of Pergamum, occupied Asia Minor and stationed two legions of soldiers on the Euphrates, the success of Mithraism in the West was secured. It spread rapidly from the Bosporus to the Atlantic, from Illyria to Britain. Its foremost apostles were the legionaries; hence it spread first to the frontier stations of the Roman army.
Mithraism was emphatically a soldier religion: Mithra, its hero, was especially a divinity of fidelity, manliness, and bravery; the stress it laid on good fellowship and brotherliness, its exclusion of women, and the secret bond amongst its members have suggested the idea that Mithraism was Masonry amongst the Roman soldiery. At the same time Eastern slaves and foreign tradesmen maintained its propaganda in the cities. When magi, coming from King Tiridates of Armenia, had worshipped in Nero an emanation of Mithra, the emperor wished to be initiated in their mysteries. As Mithraism passed as a Phrygian cult it began to share in the official recognition which Phrygian worship had long enjoyed in Rome. The Emperor Commodus was publicly initiated. Its greatest devotee however was the imperial son of a priestess of the sun-god at Sirmium in Pannonia, Valerian, who according to the testimony of Flavius Vopiscus, never forgot the cave where his mother initiated him. In Rome, he established a college of sun priests and his coins bear the legend "Sol, Dominus Imperii Romani". Diocletian, Galerius, and Licinius built at Carnuntum on the Danube a temple to Mithra with the dedication: "Fautori Imperii Sui". But with the triumph of Christianity Mithraism came to a sudden end. Under Julian it had with other pagan cults a short revival. The pagans of Alexandria lynched George the Arian, bishop of the city, for attempting to build a church over a Mithras cave near the town. The laws of Theodosius I signed its death warrant. The magi walled up their sacred caves; and Mithra has no martyrs to rival the martyrs who died for Christ.
DOCTRINE
The first principle or highest God was according to Mithraism "Infinite Time"; this was called Aion or Saeculum, Kronos or Saturnus. This Kronos is none other than Zervan, an ancient Iranian conception, which survived the sharp dualism of Zoroaster; for Zervan was father of both Ormuzd and Ahriman and connected the two opposites in a higher unity and was still worshipped a thousand years later by the Manichees. This personified Time, ineffable, sexless, passionless, was represented by a human monster, with the head of a lion and a serpent coiled about his body. He carried a sceptre and lightning as sovereign god and held in each hand a key as master of the heavens. He had two pair of wings to symbolize the swiftness of time. His body was covered with zodiacal signs and the emblems of the seasons (i.e. Chaldean astrology combined with Zervanism). This first principle begat Heaven and Earth, which in turn begat their son and equal, Ocean. As in the European legend, Heaven or Jupiter (Oromasdes) succeeds Kronos. Earth is the Speñta Armaiti of the Persians or the Juno of the Westerns, Ocean is Apam-Napat or Neptune. The Persian names were not forgotten, though the Greek and Roman ones were habitually used. Ahura Mazda and Spenta Armaiti gave birth to a great number of lesser deities and heroes: Artagnes (Hercules), Sharevar (Mars), Atar (Vulcan), Anaitis (Cybele), and so on. On the other hand there was Pluto, or Ahriman, also begotten of Infinite Time. The Incarnate Evil rose with the army of darkness to attack and dethrone Oromasdes. They were however thrown back into hell, whence they escape, wander over the face of the earth and afflict man. It is man's duty to worship the four simple elements, water and fire, air and earth, which in the main are man's friends. The seven planets likewise were beneficent deities. The souls of men, which were all created together from the beginning and which at birth had but to descend from the empyrean heaven to the bodies prepared for them, received from the seven planets their passions and characteristics. Hence the seven days of the week were dedicated to the planets, seven metals were sacred to them, seven rites of initiation were made to perfect the Mithraist, and so on. As evil spirits ever lie in wait for hapless man, he needs a friend and saviour who is Mithra. Mithra was born of a mother-rock by a river under a tree. He came into the world with the Phrygian cap on his head (hence his designation as Pileatus, the Capped One), and a knife in his hand. It is said that shepherds watched his birth, but how this could be, considering there were no men on earth, is not explained. The hero-god first gives battle to the sun, conquers him, crowns him with rays and makes him his eternal friend and fellow; nay, the sun becomes in a sense Mithra's double, or again his father, but Helios Mithras is one god. Then follows the struggle between Mithra and the bull, the central dogma of Mithraism. Ahura Mazda had created a wild bull which Mithra pursued, overcame, and dragged into his cave. This wearisome journey with the struggling bull towards the cave is the symbol of man's troubles on earth. Unfortunately, the bull escapes from the cave, whereupon Ahura Mazda sends a crow with a message to Mithra to find and slay it. Mithra reluctantly obeys, and plunges his dagger into the bull as it returns to the cave. Strange to say, from the body of the dying bull proceeds all wholesome plants and herbs that cover the earth, from his spinal marrow the corn, from his blood the vine, etc. The power of evil sends his unclean creatures to prevent or poison these productions but in vain. From the bull proceed all useful animals, and the bull, resigning itself to death, is transported to the heavenly spheres. Man is now created and subjected to the malign influence of Ahriman in the form of droughts, deluges, and conflagrations, but is saved by Mithra. Finally man is well established on earth and Mithra returns to heaven. He celebrates a last supper with Helios and his other companions, is taken in his fiery chariot across the ocean, and now in heaven protects his followers. For the struggle between good and evil continues in heaven between the planets and stars, and on earth in the heart of man. Mithra is the Mediator (Mesites) between God and man. This function first arose from the fact that as the light-god he is supposed to float midway between the upper heaven and the earth. Likewise a sun-god, his planet was supposed to hold the central place amongst the seven planets. The moral aspect of his mediation between god and man cannot be proven to be ancient. As Mazdean dualists the Mithraists were strongly inclined towards asceticism; abstention from food and absolute continence seemed to them noble and praiseworthy, though not obligatory. They battled on Mithra's side against all impurity, against all evil within and without. They believed in the immortality of the soul, sinners after death were dragged off to hell; the just passed through the seven spheres of the planets, through seven gates opening at a mystical word to Ahura Mazda, leaving at each planet a part of their lower humanity until, as pure spirits, they stood before God. At the end of the world Mithra will descend to earth on another bull, which he will sacrifice, and mixing its fat with sacred wine he will make all drink the beverage of immortality. He will thus have proved himself Nabarses, i.e. "never conquered".
http://www.newadvent.org/cathen/10402a.htm