Super Star Destroyer was an umbrella term used by both the Galactic Empire and the Alliance to Restore the Republic to refer to several classes of massive Imperial vessels larger than Imperial Star Destroyers, the largest of which was the Executor-class Star Dreadnought.
Around the time of the Battle of Endor in 4 ABY, Rebel Alliance Intelligence Service estimated that the Empire had more than a dozen Super Star Destroyers including Darth Vader’s flagship Executor, the Annihilator, the Arbitrator, Emperor Palpatine’s personal ship Eclipse, and the Ravager. However, the true number remained a subject of debate. Following the Battle of Endor, Alliance analysts endeavored to make sense of Imperial propaganda and investigate the black budgets which concealed the late Emperor’s secret weapons programs. Vader’s flagship Executor was destroyed during the Battle of Endor when an RZ-1 A-wing interceptor crashed into its command bridge, ultimately sending it crashing into the second Death Star.
By 5 ABY, Grand Admiral Rae Sloane estimated based on a study of the Imperial Navy‘s records on Coruscant that the Empire had thirteen Super Star Destroyers including Dreadnoughts in service before the second Death Star was destroyed. These included Vader’s lost flagship Executor and her own command ship Ravager, which was actually commanded by Fleet Admiral Gallius Rax. Studying the registers, she also discovered that the Rebel Alliance’s successor, the New Republic, had captured three Super Star Destroyers. Of these ships, two admirals had surrendered their vessels and personnel while the third had been stolen by New Republic forces while undergoing repairs above Kuat.
Sloane also discovered that New Republic forces had also destroyed another five Super Star Destroyers in combat by taking advantage of the ships’ understaffed crew and poor maneuverability. Grand General Cassio Tagge‘s former flagship Annihilator was taken over by pirates led by Eleodie Maracavanya. Meanwhile, the Arbitrator was destroyed by a gravity well while making a bad hyperspace calculation in an effort to evade New Republic ships. While the Emperor’s flagship Eclipse had purportedly been destroyed by the New Republic Defense Fleet, Sloane discovered that the report did not match the vessel’s black box recording. As a result, she deduced that the ship had mysteriously disappeared.
The Ravager was destroyed during the Battle of Jakku when the New Republic’s Starhawk-class battleship Concord managed to use its powerful tractor beam to drag the Super Star Destroyer down to Jakku’s surface. Meanwhile, Eleodie rechristened the Annihilator as Liberty’s Misrule, which became the capital of the Sovereign Latitudes of Maracavanya, a pirate state based in Wild Space. In an effort to curry favor with the New Republic, Eleodie used the Liberty’s Misrule to attack three Imperial II-class Star Destroyers fleeing Jakku. Later, Sloane traveled with Brendol Hux, Armitage Hux, and Rax’s child soldiers into the Unknown Regions and rendezvoused with the Eclipse in uncharted space.