After the Galactic Empire learned the location of a makeshift B-wing assembly area being used by the Rebel Alliance, Relentless was dispatched to stop the evacuation of the area. Soon after arriving in the area, she launched TIE Fighters and TIE Bombers to attack the fleeing Rebel ships. However the TIE assaults were pushed back by a group of Rebel X-wings from Red Squadron, led by Commander Keyan Farlander, and the B-wing prototypes managed to make it to hyperspace.
Much later, the Habassa had joined the Alliance. In order to destroy the Relentless, Rebels and Habassa agreed to lure the Frigate Mayhem somewhere in order to capture her.
Soon after the Rebels captured some Imperial officers bound for the Mayhem and interrogated them to learn more about Relentless and her task force. They began to formulate a plan to attack Relentless, starting with the capture of Mayhem and the destruction of the Frigate Juvaini. With her task force destroyed, Relentless was left vulnerable.
After several assaults, Relentless had her TIE supplies all but wiped out. Rebels destroyed the BFF-1 bulk freighters Dotermin and Sornsen that attempted to resupply her. Another attempt for resupply with replacement TIE Interceptors was stopped above Sunaj IV.
Eventually, the Rebels led a frontal attack prior to their migration to Hoth. B-wings from Red Squadron, again led by Keyan Farlander were charged with attacking Relentless while A-wings from Blue Squadron provided escort. After using proton torpedoes to bring down her shields, Red Squadron continued the assault using laser cannon until Relentless was finally destroyed.
Relentless appears only in the game X-wing. However there were other Star Destroyers with the name Relentless and at least one existed during the same timeframe.
It is not known if the game designers intended the ship appearing in the game to be a guest appearance of that ship since the plot development did not allow for any connections to be made.
- X-Wing Collector's CD-ROM: The Official Strategy Guide