Here’s something more recent – some notes on the organization of tribes and clans for the Sartar Book.
Although individual priests might be on the tribal ring, they usually are there as representatives of the main temples. At the tribal assembly all the priests can put what influence they want and have.
The Rex is the leader of the tribe. He or she is the head of the Orlanth cult, war leader, and the one who speaks with the tribal spirit.
We often translate the title of the Rex as “king” but it literally means “(Divinely-sanctioned) Leader.” Denotes the incarnation of Orlanth Rex. Often synonymous with King or Prince, but not always. See also City Rex.