The Mediator-class was over half the size of the prototype Viscount-class Star Defender Viscount and was a successor to the previous generations of Star Cruisers, including the MC80 Home One type, itself at one point the largest warship in the Rebel Fleet.
Like previous Mon Calamari cruisers, they were heavily but conventionally armed with turbolasers and ion cannons, defensive shields and heavy armor, tractor beam projectors, and squadrons of starfighters. Little is known about their overall layout, but one of the ship's main hangar bays had an opening on the ventral side of the hull.
The armor inside the ship was strong enough to prevent complete destruction of the vessel even in the case of a nuclear detonation inside a hangar. This was in sharp contrast to Imperial designs like the Imperial-class Star Destroyer, which could be destroyed with a similar charge placed in a hangar.
The Mediator-class ships were designed after the Black Fleet Crisis as more powerful successors to the previous classes of Star Cruisers built by the Mon Calamari Shipyards, along with the larger Viscount-class. The class also represented a move away from the alphanumeric designations which had been given to previous Mon Calamari ship-types, such as the MC80 and MC90. Instead, they used a conventional class-name based on the name of the lead ship, the Mediator.
The new battle cruisers were introduced during the Osarian-Rhommamool conflict prior to the Yuuzhan Vong War and saw service in the opening months of the galactic invasion. The class's namesake, the Mediator, can be considered the first major combat casualty of the conflict: while she was deployed to intervene in a dispute between the planets Rhommamool and Osarian, enemy infiltrator Nom Anor detonated a shuttle laden with nuclear explosives in her hangar section, severely damaging her.
In the first months of the war, military analysts like Ayddar Nylykerka, the New Republic's head of Fleet Intelligence, believed that the Mediator-class ships already in service, when used in conjunction with Bothan Assault Cruisers and Star Defenders, were sufficient to engage the Yuuzhan Vong successfully, and a Mediator-class ship was the centerpiece of a battle group of New Republic and Imperial Remnant warships deployed at Ord Mantell early in 26 ABY, in anticipation of a Yuuzhan Vong strike there.
However, during the Battle of Ord Mantell, this ship was destroyed after a vicious close-combat engagement with several enemy vessels, including a Miid Ro'ik. Not much is known of them after this event.
Although Mon Calamari was believed to have been cut off before the end of the first year of the war, it appears that secret hyperlanes were in fact kept open, and that new ships continued to be supplied to the New Republic fleets—including the Mediator-class vessels to replace those lost and damaged in the opening stages of the conflict.
A number of Mediator-class ships were part of the combined Alliance fleet guarding Mon Calamari and its shipyards in 29 ABY. The ships served under Admiral Traest Kre'fey during the Defense of Mon Calamari and were also part of the final assault of the war during the Battle of Yuuzhan'tar.
The size of the Mediator-class battle cruiser is uncertain. A lower limit is provided in The New Jedi Order: Agents of Chaos I: Hero's Trial, where a ship of this class is said to be "larger" than a 1.6 km Miid Ro'ik, while The New Jedi Order: Vector Prime says the Star Defender Viscount is "nearly twice the size" of Mediator: The Viscounts length has subsequently been specified as 3 kilometers long in The Essential Guide to Warfare, which could suggest the Mediator somewhat over 1,500 meters, or alternatively not be connected as the half-length comparison was set prior when the Viscount was 17 kilometers.
- The Complete Star Wars Encyclopedia
- The Essential Guide to Warfare