Prophets were leaders of the D'ni Church of Yahvo with the role of perceiving and speaking Yahvo's will. Prophets were usually female, as women were considered to be better able to communicate with Yahvo.
Prophets older than 125 years old (the Age of Wisdom) served as advisers to the Kings. This tradition began with King Shomat who had been an unstable ruler until he was given a prophet to advise him in 400 DE. Due to the fact that the Church of Yahvo taught that people should seek to conform to the teachings of Yahvo in all aspects of life, the prophet was able to advise the King in all matters.
However over time the prophets assigned to kings slowly lost their power and were rarely consulted, instead acting mostly as figureheads. This turned around during King Me'emen's reign with the prophet Trisari being consulted a lot after the death of King Me'emen's son.
One stricture placed on prophets that advised the kings of D'ni was they abstained from having an intimate relationship with the king. This was because it was believed that it would impede both the prophet's ability to provide advise untainted by emotional ties.