From the Back of the Book:
Ranging from the Spiderfell in the north to the Straits of Aerele in the south, Medoere was born of faith and the blood of revolution. As regent, you fulfill the duties of Archpriest of the Church of the Celestial Spell, leading the theocracy to greater heights of glory. The domain is yours to command--if you have the courage, the conviction, and the blood of kings in your veins.
This BIRTHRIGHT domain sourcebook is designed for players who want to take the role of Archpriest. It may also be used by players playing vassals to the regent, or adventurers who want to explore the mysteries of the theocracy.