The Ring Builders, also known as simply the alien civilization, were a technologically advanced extraterrestrial species whose vast interstellar empire once spanned a great portion of the Milky Way galaxy. They engineered the protomolecule as a means of spreading a network of Ring gates throughout the galaxy, effectively enabling faster-than-light travel between star systems. Their empire lasted for an unknown but presumably immense span of time, until they were wiped out by a mysterious hostile agency.
At some point after building their empire, the Ring Builders were driven to extinction by an unknown entity. Current evidence suggests that the construction and use of the rings may have drawn the aggression of these unknown entities. Dr. Okoye hypothesizes that the Ring Builders' extinction was ultimately caused by the ability of their enemies to "shut down" consciousness, which the biology of the Ring Builders was unable to compensate for. Further evidence revealed war may have been the catalyst that brought about the demise of these ancient civilisations.
After the discovery of the protomolecule on Phoebe, scientists at Protogen concluded that the moon was in fact a weapon designed by an alien civilization, launched into the Sol system with the intent of infecting primitive life on Earth with the protomolecule.
After the Ring was activated by the Y Que, it was revealed that the Ring was part of a vast network of wormhole gates leading to the Slow Zone and Ring Station. This network had been built and used by the alien civilization billions of years past, but no evidence of their continued existence remained in the Slow Zone.
The Investigator and James Holden discovered a device within Ring Station that granted them access to records detailing the alien civilization's disappearance. It appears that the civilization had at one point stretched across the Milky Way Galaxy, and possibly beyond, and existed as a sort of hive mind or collective consciousness. At some point, an unknown agent began to "kill" portions of this hive mind, severing its connection to its component star systems.
The civilization used the Ring Station to destroy the "infected" star systems by sending beams of energy through the Rings, causing the stars to explode and vaporize that system's Ring and planets. This proved ineffectual, however, and eventually the civilization enacted a quarantine by deactivating the remaining Rings. Whether through this action or those of the unknown aggressor, the alien civilization was subsequently rendered extinct.
Events on Ilus following the arrival of the Rocinante revealed further information about the nature of the alien civilization and its collapse. It appears Ilus was once used to generate energy for other parts of the alien civilization with a variety of structures having been embedded in the planet for this purpose. In one such structure, Holden and the Investigator discovered the Void bullet which appeared to have been left behind by the unknown agency responsible for the alien civilization's collapse.
While Elvi Okoye studies the Dead systems onboard the Falcon, she encounters the Adro Diamond, which is a Jupiter-sized spherical diamond theorized by Elvi Okoye to be a massive data storage device. Elvi also theorizes that, unlike with human biology, the consciousness of the Ring Builders was not linked to physical matter. Furthermore, based on the work of the repair drones on Laconia and their resurrection of Xan and Cara, Dr. Okoye speculates that the Ring Builders life cycle consisted only of a single mature form or a hive mind, as the resurrected children do not age or mature like normal humans and are connected to a source of information called The Library.
Although very little is known about the alien civilization or its disappearance, the artifacts it left behind indicate a level of technological sophistication far beyond the greatest achievements of human science and engineering. Some of their most notable creations include the protomolecule, the Ring, the Slow Zone, Ring Station and the structures permeating Ilus, as well as the planet itself, to some degree.
Based on the nature of the protomolecule and the presence of animal-like biomechanical devices on Ilus and Ring Station, Dr. Elvi Okoye concluded that the alien civilization had great respect for the power of self-replicators, such as DNA-based life, and based much of their technology around such molecules.
Many devices left by the alien civilization exhibit abilities that seem to manipulate fundamental physical properties. For example, the protomolecule-infected Eros Station was able to "dodge" the incoming Nauvoo without any apparent thrust or acceleration, and Ring Station was able to generate a field within the Slow Zone that prevented objects from exceeding a certain velocity. Additionally, the defense system on Ilus demonstrated the ability to nullify nuclear fusion within an unknown radius of the planet, preventing the ships in orbit from leaving.
Main article: Ring Builder Empire