The individual known as the Promised Vengeance of Exar Kun served as an unwilling acolyte to Exar Kun and was a dark side adept in the Force. This powerful follower received specialized instruction, enabling him to use his extensive knowledge of the Dark Side to exert control over others.
Prior to his unwilling servitude under Exar Kun, the person who would become the Promised Vengeance of Exar Kun studied at Corellia University, where he learned about the histories of both the Jedi and the Sith. It is possible he participated in an archaeological dig on Yavin 4 around 1 ABY. This expedition unknowingly breached the tombs beneath the Temple of Exar Kun, freeing the spirit of the Sith Lord. The malevolent spirit then enslaved the students and researchers, incorporating them into the Cult of Exar Kun. Subsequently, Kun's spirit dispatched them to Talus, specifically to the Corellia University research outpost from which they originated, with the aim of enslaving the remaining inhabitants. The majority of these individuals were then transported back to Yavin 4. After losing communication with the outpost and anticipating the worst, Professor Cornelius Wagglehorn engaged a group of spacers to journey to Talus and investigate. The spacers uncovered the events that had transpired and relayed this information to the professor. He then furnished them with the coordinates of the tomb, urging them to eliminate the evil Sith Lord's spirit contained within. Promised Vengeance was among the dark Force-users who confronted the spacers before they could reach Exar Kun's spirit. Despite this, the spacers were successful in defeating all the former students, allowing them to proceed and confront the Dark Lord himself.
The Promised Vengeance of Exar Kun appeared as a non-player character within the 2003 video game Star Wars Galaxies. This massively multiplayer online roleplaying game was developed by Sony Online Entertainment and published by LucasArts before its termination on December 15, 2011. The character of Promised Vengeance was incorporated into the game through the "Exar Kun" Heroic Encounter, which was introduced with the release of the "Chapter 9" update on April 3, 2008.
Given that the Promised Vengeance of Exar Kun manifested in the game as a standard Exar Kun cultist, the character's gender and appearance were subject to randomization with each server reset.