The Gyges Raiders, named for their ability to become invisible at will(cloaking device), control 16 sectors and border 6 major powers in their region of the Milky Way(Via Lactea). Their social structure is made of three core species but their exceedingly advanced technology has lead some to speculate that there is a fourth that runs the show. The lowest in their order are the Korbans, little more than mindless brutes that they never seem to run short of. In the middle are the species called the Gyges themselves, a culture built around stealth and hunting but possessing no concept of honor, although their cunning and accuracy with their weapons is legendary. The third and rarest of the three known species are the Nyarl, they appear to give the orders and the rewards but while devious, they appear to be similarly devoid of understanding in the underlying principles of their technology. Technology that in some cases includes cloaking devices and thousands of tiny drone harvesters as well as regenerative hulls and powerful directed energy weapons for their ships.
There are thousands of worlds within their territory with minor civilizations and they are at the mercy of semi-regular raids that destroy any fleets they might build and take seeming random sentients prisoner, never to be seen again. They tend to attack anything that comes within view but only stray from systems with their "star-harnesses" when placing more of the mysterious structures or attempting to gain more territory in which to expand this endeavor.
They are considered the greatest threat to the League of Fringe Worlds and M-Con forces fight them in border skirmishes on a regular basis. To the Hesiod Kingdom(controlling one sector in the midst of Raider Space) however, they are the perfect buffer against any other hostile species that may come looking for them.