Great Sun

The Great Sun, or in Elder Speech, Ard Feainn is according to Wiedźmin: Gra Wyobraźni the major religion in Nilfgaardian Empire since the rule of an unknown Emperor preceding Fergus. According to the World of the Witcher (book), the inhabits of the Northern Kingdoms know very little about the cult of the Great Sun. The head of this religion is a high priest, which may also be the Nilfgaardian emperor.

Wiedźmin: Gra Wyobraźni
''The cult of the Great Sun were formerly only one of various religions in the Empire, popular rather only in itscore regions. The situation changed during reign of the predecessor of Emperor Fergus, about fifty years ago, who initiated a series of major reforms. The ruler was looking for a symbol which would unite the realm better and more permanently than only the ruling dynasty. By skillfully managing with cash and giving priests his monarchic favor, he made that the cult began to gain a new crowds of followers in the whole Empire. In exchange for it, Emperor demanded an absolute support for his policies from the clergy, practically making priesthood another form of civil service.  Then the monarch issued a special decree called "March 8th Edict" which granted the cult to the status of official state religion. Though during reign of the Usurper its rights were diminished, its position even increased after Emhyr var Emreis and his army overthrew the usurper.'' ''The cult has its roots in elven cult of nature. The primary deity is Sun, giver of warm and life, protector of the humankind, but also being able to be cruel and destructive. Since the "March 8th Edict" it has been also a patron of the ruling dynasty. The most important holidays are the Equinoxes and birthday of actually ruling Imperator, currently July 26. The central ceremonies hend in the capital, performed by the Imperator as a High Priest, head of the religion. All holidays are celabrated with great pomp, to the accompaniment of solemn music and in the presence of all major officials, commanders and aristocrats. After oficial ceremonies, folk games with food and beverage take place. It is noteworthy that a number of customs related with holidays are derived in a straight line from elven tradition.''

Priests of the cult wear white raiments embroidered in gold and silver during devotions, celebrations and holidays; as casual clothes they wear black civilian dress.

Trivia

 * In The Witcher 3: Wild Hunt there is armor called Great Sun armor.