The Priestess

The Priestess' Myriad Cathedral is a home to every faith, except the Druids, who hate civilization.

The Priestess serves the Gods, who have laid down a just and right way for people to live their lives. She commissions great works from the Imperial Architects, of stone rising to honor the Sun and the Sky. One day those spires shall each fall, and so Death is likewise honored.

Investiture

The original Priestess and Crusader were the first mortals created.

The title gets handed down, but the rite of investiture that makes the new one "The Priestess" and connects her to the source of divine magic also gives her the perspective bestowed on her ultimate predecessor by the gods, and that tends to wash out most of her own personality. What's left of the personality imprints itself on that perspective, so it becomes a mixture of divine paradigm and all of the predecessors. Nobody can know what the original template was, because the gods don't talk about it.

The gods all contributed a portion of their essence to create a pool of divine power. Becoming a Cleric is partially learning how to tap into that power. Every cleric has a permanent link to that pool, which scholars call the Source. By some of the oldest Oaths, the gods can't control who gets how much. Experienced Clerics learn to safely handle more. A neophyte could open themselves to as much power as the Priestess herself, but would be charred to ashes by the power before getting any kind of control of it.