Alliance Intelligence had revealed that the Imperial II-class Star Destroyer Corrupter was damaged and unable to move. This likely occurred during the Battle of Hoth. Due to extensive search efforts, they had little time to conduct the necessary repairs. The Alliance intercepted communications between the Corrupter and the frigate Monitor that revealed a convoy that would deliver new shipments to complete the repairs. The Rebels decided to send a strike force to destroy the convoy.
The Rebel fighters arrived at the Bettel asteroid drift where the convoy was attempting to reach hyperspace. The Assault Gunboats attempted to stop the fighters but were unsuccessful. The repair convoy was then successfully destroyed but the Monitor escaped into hyperspace. The Rebel fighters chased it into the Mev system, where the Corrupter was waiting for a repair convoy that was already destroyed.
The Monitor released all four Lambda-class T-4a shuttles, which carried hyperdrive technicians, and its starfighters for cover. But that was ineffective as the Monitor made the mistake of releasing the shuttles too far away from the Corrupter and all were destroyed. The Rebel starfighters likely pulled back as they were prompted to by Alliance Command.
The attack was a huge success for the Rebels. They were then ready to make the final stage to escape the Imperial forces searching for them. With the convoy destroyed, the Corrupter was still stranded by the time the Rebels escaped into hyperspace and into another sector in space. In fact, the Corrupter had barely finished repairs, but the hyperdrive was still not working when they attempted to return to Coruscant.
It is possible for the player to destroy the Monitor. Since the ship doesn't appear anywhere else in the game and no other source, it is likely it was destroyed.
The player can also attempt to destroy the Corrupter, however unlike the case of Monitor, the scenario demands the ship to appear again later. In order for the continuity to be maintained, if the player brings the Corrupters shields down, TIE Avengers from Avenger Squadron appear. They are armed with Concussion missiles and can be difficult to defeat, ensuring therefore the survival of the Corrupter.