Church of the Unconquered Sun

The  was a religious organization, powerful in certain Histories, which worshiped the Sun-in-Splendour. In addition to the Sun itself, the Church venerated its Names, including the Madrugad, the Meniscate, and the Sun-in-Rags, which would later become Hours after the Intercalate. Just as the Intercalate divided the Sun itself, it caused a schism within the Church, resulting in the Church's fall from power.

Its highest rites were performed in the Concursum. All of its priests were officially male, but women could ceremonially become male to join the priesthood. The Church's funeral rituals honored the Madrugad, and included a caution that all blades should remain sheathed 'lest the corpse be not quiet.' This may be a reference to the Shattered Risen.

Sisterhood of the Knot
In some histories, the Sisterhood of the Knot influenced the Church, which came to acknowledge their Hours as well as the Sun-in-Splendour in its Concursum rites. This was controversial within the Church, leading Hieronymus Pseudo-Hypnerotomachus to write a denunciation of their Hours and especially the Thunderskin.

War of the Roads
In the War of the Roads, the Church joined forces with the Sisterhood of the Knot to defend against the Leashed Flame. The Leashed Flame were defeated, but at incredible cost - though the Sisterhood's martyr-soldiers were burned by the Sovereigns of the Leashed Flame, the Flame was unleashed and devoured the Sovereigns.

Trivia

 * "The Unconquered Sun", used as an epithet of the Sun-in-Splendour, is a translation of the name of the late Roman solar god, Sol Invictus, who in turn was possibly related to the earlier solar god Elagabalus, also mentioned in-game.