Domum Regimen is the capital of the Second Galactic Senate. It orbits the star Sol Regimen. It is also the site of the Battle of Domum Regimen, an event that lead to the creation of the Second Galactic Senate's calendar system.
Domum Regimen has its origins as a server node for Na'zrah during the era of the Arckasians. Like Novarckas, it hosted many of Na'zrah's key functions and served as a way for it to reach out to people in the Crucible Galaxy. They are effectively large megastructures - the largest of which double as Dyson spheres, but Domum Regimen was comparably smaller about the size of a small moon.
During the era of the Omni Empire, many of Na'zrah's server nodes became corrupted into LUCIS nodes. Domum Regimen soon became the last Na'zrah server node, and to protect himself, Na'zrah went offline leaving LUCIS to claim much of the galaxy. At least until the creation of Infra and subsequently the Buyuk.
During the Buyuk's extermination of the Omni, the Buyuk themselves continued to hunt down other traces of Na'zrah to extinguish him for good, but they did not destroy him on Domum Regimen. As Na'zrah had gone dark, they had thought he was already dead, so the Buyuk instead took control of the area to make use of the large number of jumpgates present.
After the Arkarnas offensive towards the Buyuk and the declaration of a stalemate, Domum Regimen became the seat of the First Senate. With the Buyuk having been driven away, the Arkarnas made an effort to study the space station. Na'zrah, sensing the lower levels of hostility, began its rebooting process to activate itself. However, his functions were extremely limited as Na'zrah had gone millions of years without activity. The Arkarnas worked to restore as many functions of Na'zrah as they could.
However, before the Arkarnas could finish their work, the Second Galactic War struck leading to the dissolution of the First Galactic Senate. With the Arkarnas now out of the picture, the Buyuk took the liberty to recapture Domum Regimen. They were now aware of the presence of Na'zrah, but rather than destroying him as their original purpose commanded, INFRA believed that studying Na'zrah's systems could lead to him figuring out how to reactivate LUCIS as LUCIS was based on Na'zrah's operating system. INFRA discovered that linking itself to a jumpgate to the planet Debesis might be able to wake up LUCIS, but he did not have the resources to act on this as only shortly after, a joint alliance between the UESS, Karalian Empire and other factions began to invade Domum Regimen. As such, INFRA could only devise a backup protocol to signal sleeper agents to reactive the Debesis jumpgate in the event INFRA were to fail.
During the invasion of Domum Regimen, Na'zrah chose the side of the UESS/KE alliance. Now more active thanks to the Arkarnas's efforts and to an extent the Buyuk's, Na'zrah had almost complete control of Domum Regimen using his interfacing with Domum Regimen's hardware to drive out Buyuk forces. Because of the large amount of jumpgates in the area, the alliance now had control of a major waypoint of the galaxy where many civilizations from all over could meet. Thus formed the Second Galactic Senate.