The Siren Hymn Temple was the territory of the Siren Race. Unlike the Empires, they didn't have cities or nobles titles; instead, they all worshiped the Mermaid Goddess. They divided their territory into regions, and Priest Lords were anointed to govern those regions.
Priests govern smaller regions and are responsible for both religious and secular matters. Some may owe allegiance to a central High Priest, and some may operate with more autonomy.
This local control allows for a better understanding of regional needs. However, there is potential for conflicting interpretations of doctrine and power struggles between Priest-Lords.