Ancients

Ancients (also known as Ahshuri) are one of those few species that are believed to be truly alien, not connected to humans in any way... and because of that hard to truly understand or comprehend. They are also one of the most powerful and technologically advanced species in the known part of the Galaxy, that is however considered to be extinct. Probably.
They are responsible for creation of the Greys that turned out to be the cause of their downfall. Their vanquishers, despite living for thousands of years alongside the so called Ancients (called by them Ahshuri) have very little knowledge of their true nature, not even knowing how they looked like.

Civilization and Culture

Average Technological Level

Ancients were one of the most advanced of known species, with especially their energy weapons and electronics being on almost completely different level than achievements of today. Despite their technological stagnation they seemed to be able to construct megastructures - including several ringworlds and a single, almost finished Dyson Sphere, all of which fell into ruins after the Ahshuri disappearance due to Greys lack of knowledge necessary to sustain them.

History

It is believed that the Ancients originate in the so called Ahshuri Cluster in the western Scutus-Centaurus Arm, that today is controlled by the Grey Empire. Exact date of their rise is unknown, however it is believed to have correspond with the decline and collapse of the Silinrul Empire, that seems to have retreat completely from the Cluster completely about BC 5400. It is unknown if the retreat was cause by the Ahshuri expansion, it is however very possible.
It is also believed that even at this point the Ancients were truly ancient. There is an undeniable proof that they were around (and had no problem travelling to Earth) at least BC 25 000 (if not earlier). It is believed that they predated the rise of Silinrul Empire and used to control significant part of Southern Milky Way before suffering a mysterious collapse, to reappear again around 5400.
Very little is known about first Ahshuri Empire, besides the fact that they visited Earth and kidnapped a significant number of Homo Neanderthalensis. Those kidnapped humans became a source of Greys, a servant species of Ancients. They were used to do a more menial parts of running an Empire, including menial work and serving as footsoldiers. Both species had very little in common, living in complete separation.
After (probably) pushing Silinruls out of Ahshuri Cluster their Empire entered a period of stagnation. The reasoning for it is unknown, Greys population was obviously growing but seemed to have been repetitively culled by the Ahshuri for no apparent reason. This continued until BC 1800 (a period of stagnation that was almost unprecedented) when the Grey Rebellion occured.
The treatment they received from stagnated Ahshuri slowly infuriated the Greys - that couldn't even voice their complaints because of the absolutely perfect separation between the two species. No Grey ever saw an Ahshuri. All orders came through computers, the communication being completely one directional. Even warships were perfectly separated. This caused a growing dissent and, finally, a Grey Rebellion. Greys simply stopped working and listening to orders, that soon stopped coming. After storming the Ahshuri quarters the servants found nothing. Everything was stripped clear, without even slightest amount of biological material. Despite the computers obviously programmed to transfer orders written by an existing species - it definitely wasn't an autopilot.
No Ahshuri were ever found, and their disappearance haunts Greys to this day. Some believe they never existed, others think that they were in fact Greys that overthrew the Ahshuri millenia ago, but kept the facade and then simply disappeared in the masses of victorious servants. Many believes that they understood that their era has finished and either ended their lives or departed somewhere beyond the Cluster. But some believe that there are still out there, watching...