A YJA Moment - The War Worlds of Cybertron

 The revelation that the Warworld piloted by Vandal Savage was created by Cybertronians came as a shock to the Mythic Avengers, but it had the effect of revealing a previously unknown era of Transformer history. In the time before the All-Spark, the robot servants of the Quintessons served the Infinite Empire.  They were based on the artificial factory-world of Cybertron, which made numerous products for the growing Rakatan military.  Amongst them were giant Battle-Spheres which were intended to serve as mobile bases for the Infinite Empire fleet.

The original Battle-Sphere prototype, code-named Nul, underwent extensive trials against the neighbors of the Infinite Empire. It was slated to be officially transferred to the Imperial fleet, when its commander staged a rebellion, using Nul against Rakatan ships which had been escorting it.  After leaving a swath of destruction across the entire Empire, where he was pursued by the entire Infinite Empire armada, he took the Battle outside Known Space.  It would be many centuries before Nul would return, piloted by the alien Mongol as Warworld.

The loss of Nul caused ripples throughout the Empire, including Cybertron.  The leadership of the Rakatan completely halted further development of the Battle-Spheres, leaving the future of the other three prototypes Unias, Binar, and Trion uncertain.  To prevent further incidents, the Quintessons were ordered to disable the propulsion and centralized control systems from all the Battle-Spheres immediately.  This forced them to repurpose the satellites for other purposes.

Unias, the largest of the Battle-Spheres, was redesigned for matter-processing.  Large planetoids or other mineral-rich debris were funneled to Unias so it could be ground down, sorted, and smelted into any useful metals or other elements.  Over time, a central control unit was installed similar to the one utilized in Cybertron in order to improve coordination and efficiency.  This proved disastrous during the Prime War when Unias was turned against the rebel Transformers.  Primus used the power of the All-Spark to grant sentience to the Battle-Sphere, creating Unicron, which proceeded to devastate the Quinesson forces before leaving for parts unknown.

Binar and Trion were only partially completed when construction was ended, and neither the Quintessons nor the Transformers seemed to be interested in rendering them operational.  Instead, they transitioned to be expansion areas for the Transformer population, with much of their combat systems replaced with habitation and manufacturing areas.  During the Great War between the Autobots and Decepticons, the moons were considered a great prize by Megatron, who sought to mount orbital weapons on them to strike at Autobot cities on the main planet.