The Harbinger-class ultra star destroyer was a massive ship type created by the Sith Dominion. Only one ship of the class, the Harbinger, was ever constructed, although it was suspected that similar, but smaller, vessels were in development as of 85 ABY.
The Harbinger-class was developed by the Sith Dominion after they saw schematics for the Destroyer Two. After years of construction and research and development trial and error, the first, and only, ship of this class, the Harbinger, was launched.
The Harbinger-class was designed to be the ultimate star destroyer, and, as such, utilized many different weapons as it's armament. The Harbinger's armament included: 100,000 heavy turbolasers, 150,000 medium turbolasers, and 90,000 variable warhead launchers, all used for ship-to-ship combat and orbital strikes. Along the central beam of the ship, situated at the bow, was a 5,000 megaton superlaser capable of cracking continents and destroying fleets.
The Harbinger-class was used as a command ship, and the only ship of the class, the Harbinger, served as the mobile headquarters for Ursula Vaiken and the Sith Dominion. The vessel was also intended to be used as a staging area for large-scale invasions.
The Harbinger-class was very similar to the Executor-class star dreadnought of times past, but with a split stern. 97 bright-red thrusters propelled the gargantuan vessel through space, while its light red hull warned enemies of its presence. The Sith Dominion used the ship's intimidating appearance to force entire star systems into submission without as much as a shot. Because of this, the gunners were not used to combat, and this became apparent during the rare occasion of a battle.
Behind the Scenes
The Harbinger-class is based on the Darth Vader's flagship, the Executor, and the Dominance SSD, which served as the inspiration for the split stern.