Mosthigh priest signified a position of great importance among the Yuuzhan Vong priest caste. Elan, a Priestess of the Yuuzhan Vong, was given the duty of assassinating numerous prominent Jedi Knights belonging to the New Jedi Order in 25 ABY; she was under the impression that if she carried out this task successfully, her father, the High Priest named Jakan, would be elevated to the status of mosthigh priest. After a Yuuzhan Vong assassin attempted to end Elan's life on the planet Wayland, she told her familiar, Vergere, that she was prepared to die while fulfilling her mission, knowing that her father would be promoted and their domain would flourish as a result.
Despite Elan's failure to eliminate the Jedi before she perished during the Battle of Bilbringi, her father did achieve greater power and standing. However, Jakan continued to be known as High Priest for the duration of the Yuuzhan Vong War.
The title of mosthigh priest was initially referenced in the 2000 book The New Jedi Order: Agents of Chaos I: Hero's Trial, penned by James Luceno.