The Thousand System Empire

"'The greatest threat to the galaxy festers among the countless stars across the core, exterminating life with excessive glee, guided by manipulative demagogues preaching the words of a dark pantheon. Should they continue on, unimpeded, there will be little for the Lhumminaar to destroy.' - Ancient Avarian Writings, dated to 438 million years ago."

Overview
The largest and oldest empire in the modern Milky Way, the Thousand Systems Empire is the domain of the Zel'gan Noctoru, spanning almost half of the entire galaxy. It spread from the midnight world of Byzanntium over billions of years, extinguishing countless thousands of civilizations in their path, as those long lost societies didn't worship the same gods as the Zel'gan.