Three Great Races

As far back as any surviving records go, we do not have any recorded history, whether inferred or explicit, on the affairs of he galaxy before the Three Great Races. Therefor, for the purposes of this record, we will call this 'the beginning of recorded time". In the beginning of recorded time, there were Three Great Races or empires that spanned the whole of the galaxy - but this too is not entirely correct either; for there was also another. The four beginning races were The Ancients, Ezsh'der the Doryu, The Darkness (also known as The Intruders and The Madness), and The Fourth Race who left this galaxy after the victory against The Darkness during the last Great Horror.
 

"Pursuing further interests indeed! More likely they grew tired of the conflict and chose the path of cowardice at the most convenient time. Be it in the destiny of all they who abandon their cause, that trouble will forever befall them time and again!"

— Nomad

  Once the Darkness lost their foothold after The Final Purge, The Fourth Race was convinced that the Darkness could no longer return and decided to move on and explore the next galaxy. One of their own ruling council members spoke ardently against this move, calling it "foolish abandonment of the gate to oblivion that we have been called to guard". After The Fourth Race left the galaxy, a wondering prophet called Nomad, wandered through Ezsh'der the Doryu space warning of the 5th Intrusion when The Madness would come again. The Ezsh'der the Doryu had suffered such great losses that they vowed to do whatever it took to prevent another Great Horror.
 

"The Ezsh'er the Doryu have not had a single member of their species born nor killed in over 300,000 years. To simply say the Ezsh'der were plummeted into an eternal abyss of misery, bleakness and woe; forever doomed to wallow in a dreary depression and an endless paranoia, would be quite an understatement!"

— Nomad

  The Ezsh'der became consumed with the idea that if they had total control over the lesser races of the galaxy, they could spot any signs of The Madness and snuff it out. The Ancients, of course, could never condone enslavement and annihilation of sentient species. The Ancients instead proposed encasing the entire galaxy in an impenetrable energy barrier that The Intruders (their own term for The Darkness) could not penetrate. Not convinced that The Ancients were capable of this enormous feat, they refused to abandon their doctrine of subduing all other alien species within their reach.
 

"The Ancients were the architects of the Great Wonders of the Galaxy, the Ezsh'der knew they could build the Frontier around the entire galaxy; to assume they just 'didn't think it could be done' is an oversimplification of deep rooted emotional pain within the Ezsh'der, which drove them into their own state of madness and paranoia."

— Nomad

  The Ancients, still recovering from their own losses, feared that if they and the Ezsh'der were no longer on good terms, there would be no way to withstand the next coming of the Intruders. So they build the Great Frontier of the Ancients around their own portion of the galaxy, forever shutting out the Ezsh'der and the Intruders. Unfortunately for The Ancients, this also proved their own downfall; in the absence of conflict and turmoil, their culture decayed and their society digressed into what we now call The Mori.