The Eclipse-class vessels were among the largest dreadnought-scale ships/Super Star Destroyers ever to be fielded within Galactic history. Although technically being dwarfed in length only by both the Executor-class Star Dreadnought and the Vengeance-class dreadnought by 1.5 kilometers, the Eclipse-class nonetheless outranked even the Executor-class in terms of overall mass and volume. Its size in addition was also large enough for it to also be classified as a space station.
Offensive and defensive systems
The most deadly weapon carried by Eclipse-class ships was an axial superlaser, similar to but significantly less powerful than one of the component beams used in the Death Star's superlaser. This superlaser was the pinnacle of Imperial destruction in their fleets.
An Eclipse's superlaser easily had the power to destroy other Super Star Destroyers, as the Annihilator found out when Tyber Zann seized the Eclipse's incredible power above Kuat.
Destroying other ships however, doesn't show the extent of the Eclipse's superlaser's power. These weapons were capable of slashing through any planetary shield to crack open a planet's crust and sear entire continental landmasses. The massive superlaser was more widely used to destroy enemy capital ships and space stations during combat.
The class benefited from the most significant weaponry-improvements of the last few decades. This included gravity well projectors and improved ion cannons. Additionally, these behemoths were armed with hundreds of heavy laser and turbolaser mountings.
In addition to its firepower, the Eclipse-class's armor and shields were so powerful that it could ram enemy ships without any risk of taking damage, and without hesitance.
The Eclipse-class was more mobile than the Death Star, being equipped with both an enhanced hyperdrive and fast sublight engines.
An Eclipse-class vessel carried 600 TIE/IN interceptors and 96 TIE Bombers, divided into 58 squadrons; for ground assault, they carried 150,000 Imperial soldiers, 100 AT-ATs, and five prefabricated bases. The hangars were located at the sides of the vessel, with the fore and aft launch bays closely spaced underneath this area, towards the middle of the ship.
Each ship of the class was crewed by over 700,000 personnel, and Eclipse II also carried a complement of Shadow Droid starfighters. Troop quarters were located on the lower frontal section of the vessel, in front of the hangar areas.
The bridge tower contained the main communications array and sensor array, located on the port side and starboard side, respectively. In addition to containing the main command station for the ship on the lower portion of the tower, it also housed the deflector shield command center, on the top area.
There were several variances between the two known vessels of this class, the Eclipse I and the Eclipse II: The Eclipse I possessed six engines on the back, whereas the Eclipse II possessed eight. In addition, the Eclipse I had the engines being separate from each other and more to the sides, whereas the Eclipse II are grouped together in a manner similar to other Star Destroyers. Lastly, the Eclipse II has a command bridge tower directly over the superlaser weapon that the Eclipse I lacked.
While the lead ship, the Eclipse, was being built, the Empire also constructed an Eclipse-class prototype to use as a weapons testbed. This craft was later converted to become the battlestation Tarkin. The Tarkin was eventually destroyed by a Rebel sabotage team in 3 ABY.
The Eclipse, alongside with its sister ship, the Eclipse II, began construction early in the Galactic Civil War, around 0 ABY. The Eclipse was built above Kuat, whereas the Eclipse II was built over Byss. The idea for both ships' hulls was derived from the look of ancient nautical warships.
By 4 ABY, both the Eclipse and the Eclipse II had its superlaser main weapon installed and in functional condition. However, both ships ended up significantly delayed in terms of completion thanks to Palpatine's demise and the power vacuum that ensued. In addition, the crime lord Tyber Zann wanted to access records on the ship, and if possible steal the ship, so he attacked Kuat and took control of the ship, and used to it to damage an Imperial and rebel fleet. Afterwards, Zann had no further use for the vessel, finding its size to be more cumbersome for laying low to even the Rebel Alliance, and left it adrift.
Later on, this ship was completed and became the reborn Emperor Palpatine's flagship, with its sister ship Eclipse II assuming the same role after the original's destruction.
Approximately 17.5 kilometers long on the keel, these jet-black battleships were among the largest Super Star Destroyers ever built, and among the most heavily armed warships of all time. In terms of scale, they were the successors to dreadnoughts like Eye of Palpatine and the Kuati Star Dreadnoughts that preceded the New Republic era.
Eclipse took almost as long to construct as either of the Empire's Death Star battlemoons, and for most of her career, she served as an orbital battlestation at Byss. At some point later, the Eclipse came out of hyperspace, to which its black hull caused some New Republic forces to initially believe that it was a ghost ship, although they quickly realized that the ship was in fact real when it opened fire to which only the information officer, Nara Dun, survived and managed to inform New Republic forces about the attack.
She was destroyed along with the reborn Emperor in 10 ABY, during an Imperial attack on Pinnacle Moon in the Da Soocha system, when Luke Skywalker and his sister, Princess Leia Organa Solo, managed to disrupt the Emperor's control of a titanic Force storm, a massive conflagration of dark side energy that the Emperor had summoned in order to wipe out the massed New Republic fleet.
After this catastrophe, the Eclipse II replaced the original. It was slightly different than its predecessor, with different thrusters. Above the planet Onderon, Lando Calrissian and Wedge Antilles led a small boarding party against the mighty battleship, and R2-D2 was able to override Eclipse II's computer banks. The astromech droid then sent Eclipse II hurtling through hyperspace on a collision course with the superweapon Galaxy Gun. Eclipse II rammed the Galaxy Gun, destroying both. One last projectile was pulled by Byss' gravity and impacted the planet, the resulting explosion annihilating Byss.