War moon

War moons are satellites converted into warships by the Hive, taken from around the orbit of Fundament after the war with the Ammonite species. They became mobile homes for the Hive species during their genocidal campaign across the universe. There were as many as fifty-two but more may have been added as time went on. At least one is mentioned to have been destroyed.

Design
The moons were hollowed out to serve as breeding grounds and training facilities, and possibly even shipyards and carriers for the Hive fleets. They were described as black, whether to cloak their thermal emission to prevent detection or through constant war.

History
First suggested to Auryx by his gods, the Hive colonized the Ammonite worlds as both an insult to them and for homes as Fundament was no longer suitable. As the Hive matured the moons were soon connected by interdimensional rifts thanks to studies done by Savathun and power from Xivu Arath, and their kingdoms grew through the establishment of their Ascendant realms, with trade and language passing between them.

To stay sharp, and feed their worms, the Hive godkings warred amongst themselves as the moons traveled through interstellar space until they reached other civilizations, at which point they united to exterminate them. War moons were used to physically destroy Taishibethi orbitals and star webs. They were also present during the Hive-Harmony war; Oryx and Savathûn conversed amongst them. After this conflict both Xivu Arath and Savathûn departed, taking their war moons with them, the former flying off into space and the latter disappearing through the black hole.

At some point during Emperor Calus' exile, he and his Loyalists have found a stray war moon that housed the Crown of Sorrow. In an attempt to bring the Hive into the Loyalists, Calus had gifted the Crown to Gahlran, the Sorrow-Bearer, who was then taken and swayed by the Hive power in the Crown, turning him against Calus. Subsequently, Calus had called for Guardians to re-enter the Leviathan to kill Gahlran.

Trivia

 * Oryx's Dreadnaught could be thought of as a war moon, as it served as a mobile base for his Hive.
 * War moons appeared to have fallen out of favor, at least amongst Oryx's brood, since none were spotted during the Battle of Saturn or anywhere. It may be that Hive warships are either modified moons or built entirely separate, or Oryx left his moons behind when he came to avenge Crota.
 * Given how the Hive have nearly hallowed out Earth's moon, its possible the Hive were planning on turning Luna into one of their War Moons.

List of appearances

 * Destiny
 * The Taken King
 * Destiny 2
 * Penumbra