The first of the Mediator-class battle cruisers, the Mediator was sent under the command of Commander Ackdool in 25 ABY to oversee the New Republic's mediation of the dispute between Rhommamool and Osarian.
Nom Anor was able to damage the Mediator after being offered sanctuary for a diplomatic meeting by Ackdool. The Yuuzhan Vong operative used a concealed A-wing to escape from the two stage liquid fuelled rocket that was bringing him to the battle cruiser. Nom Anor then remotely detonated the nuclear fission devices packed in his spacecraft as this was entering into the Mediator's lower docking bay. The explosion vaporized the entire section of docking bays, blowing out a huge section of the lower floor of the ship. Still, the vessel was not completely destroyed and managed to get its spin under control, a testament to Mon Calamari engineering.
While it is unknown whether the Mediator returned to service, her class went on to become a major part of the Galactic Alliance Defense Fleet, serving at the Defense of Mon Calamari and the Battle of Yuuzhan'tar.