The Zuxian are believed to be the progenitors of all genetically-human species in the Rutaren Galaxy Over billions of years, the Zuxian people expanded out from their homeworld (location unknown) and home system (also unknown) to colonize the galaxy.
Despite their advancements in technology, including quantum computing and faster-than-light travel, the Zuxian empire established colonies in seemingly unrelated remote worlds. It's unclear whether they intended these colonies to expand within their particular sectors and colonize other livable worlds nearby, if they were still testing their FTL technology and thus wound up at fairly random coordinates, or if they were attempting to escape some form of extinction event at home and these colonies were the 'life rafts' of one or more factions within the Zuxian.
What is known is that, in nearly every sector, the influence of the Zuxian humans died out between millions and thousands of years ago, depending on the sector. Their descendants have diverged into several known disparate population groups: the Gargorians, the Juren and the Sirian Humans Much of their advanced technology was also lost, either due to environmental factors (Gargoria) or political rebellion (Sirian).
Only the Juren still possess the highly advanced Zuxian discoveries, though due to their own historical infighting, they have long since lost records of most of the remote 'life boat' colonies throughout the Rutaren galaxy.
It's unknown whether the Zuxian still exist in anything but their technology and their descendants, but their legacy (and the myths surrounding it) still echo throughout disjoint sectors of the galaxy.