Liberty's Misrule was an Executor-class Star Dreadnought formerly known as the Annihilator while serving as the flagship of Grand General Cassio Tagge in the aftermath of the Battle of Yavin. It was later captured by the pirate Eleodie Maracavanya, who expressed distaste at the name Annihilator, and renamed the vessel Liberty's Misrule.
Two years later, in 2 ABY, Imperial Grand Moff Tobias Rune pursued this vessel into Wild Space with the intent of claiming it as his own. Tobias used a one-use biological disruptor superweapon known as BDDE, or Biological Disintegration Decoy Explosive. The weapon took the form of an Imperial Cargo Ship rumored to be carrying one of Palpatine's priceless artifacts from an unknown world. Eleodie Maracavanya captured the decoy and once it was brought inside the main hangar of the vessel, the decoy detonated; disintegrating all organic life on board.
Tobias later used the HoloNet Transceiver to remotely gain control of the vessel and tow it back to Andor Prime where it would be retrofitted and remodeled. He named the vessel Guardian. The command superstructure was replaced by a modified LH-1740, also known as Lucrehulk-Class Modular Control Core. Its outerhull was reinforced with a coating of Titanium-Reinforced alusteel armor. This vessel was then painted a reflective black, allowing it to blend in easily with the vacuum of space, and was even equipped with a cloaking device along with the rest of his fleet.
In 3 ABY, Tobias used this Super Star Destroyer to threaten a member of the Hutt Council to turn over a rumored Jedi Padawan which was tucked away inside a stasis casket. The Jedi Padawan turned out to beKraytia Zarin, a Dark Jedi who escaped Order 66 and fled to the planet of Orto Plutonia to escape Imperial Inquisitors. Using offworld assets, she was able to purchase parts build a stasis casket and put herself inside. The only reason she fell into Hutt hands is because rogue Pantoran scavengers sold the casket since they couldn't open it without using the force.
The Guardian made its official debut at the Battle of Endor, where it would flee the system before Admiral Rae Sloane could give the order. It resurfaced three weeks later in the planetary system of Naboo with his entire amassed Oversector Defense Fleet as a trap for Operation Cinder. He proceeded to capture Queen Sosha Soruna, Princess Leia Amidala-Skywalker and Shara Bey during their defense of Naboo. Where he forced an engagement between himself and the Naboo Monarch.