The cult of Sol deities combined with the influence of Eastern religions led to the uprising in the third century CE. a new worship of the syncretic deity “Invincible Sun” (deus Sol Invictus). The cult Sol Invictus was a new syncretic cult combining elements of Mithraism, worship of El Gabal, Baal, Astarte and the Roman solar deity Sol. God, the personification of all other deities, was worshiped by many Middle Eastern cities.
The cult Sol Invictus was celebrated at the end of the empire (principate) and was introduced by Emperor Aurelian. It was primarily aimed at rebuilding the divine majesty on which power was to be based from now on. The country was experiencing times of crisis in the third century CE and a power grounding tool was needed. However, we can see the beginning of the cult of deus Sol Invictus in the empire during the reign of Emperor Gallienus, who ordered the construction of a large statue of Sol on Esquliline Hill. However, it was Aurelian who gave the status of the most important deity of Rome Sol Invictus. It is worth noting that the new deity not only ruled over the human world, but also the pantheon of other gods. From that moment the emperor became a messenger of God. Aurelian had the coins minted Sol, on the obverse, and the emperor was titled “god and lord of birth” (deus et dominus natus). As you can see, the emperor Aurelian became the divine representative of the “Invincible Sun”. Any attempt to overthrow the ruler and raise his hand on him was sacrilege.
The cult Sol Invictus maintained emperor Aurelian. By decree of March 7, 321 CE Emperor Constantine the Great introduced Sunday as the official holiday of Sol Invictus – dies Solis. The celebration of Sol Invictus, which falls on December 25, is first certified in 354 CE. Church at the end of the 4th century CE. rewrote the celebration of this Christmas day. It is widely claimed that December 25 for Christmas was chosen to deliberately remove and replace the Rome festival Dies Natalis Solis Invicti (“The birth of the invincible sun”). However, this claim is criticized.