and it begins

Okay, first things first, I guess I will begin by painting a little corner of the big picture.
The universe is, as far as we can tell, about fifteen billion years old. For the last ten of those the big cluser of stars and gasses that we call the milky way has been a happening thing. In the first couple billion of those years 99 and a lot of more nines out of every hundred atoms in the cluster were either hydrogen or helium and essentially all of the remainder were lithium or some other really light element. (Actually, I can't remember if lithium is stable enough to have been even a trace component of the stuff left over from the first year or so of the universe. I know one of the ultra lights wasn't.) Well ten billion years ago, that big ole cloud of dust started to coalesce into stars, mostly big ones made almost entirely of hydrogen and helium. Not a lot to work with if you want to deal with living things. But they did start fusing that hydrogen and helium into much more interesting elements, like lithium and nitrogen and carbon and oxygen and really all of the elements on the periodic table up to and including iron. After that though they pretty much stopped. You see when you slam two nuclei together and create a third, larger nucleus, it takes a little bit of energy and gives off a little bit of energy. If you are making things like neon or sodium or carbon, you are putting out more energy than you are using. On the other hand, when you slip over the line from iron to cobalt, suddenly it is takning more energy to form the new atom than is liberated by the formation.
All of those intersting things like Nickel and copper and gold and zink and uranium are formed under other conditions, like when a star explodes. None of them were in the first set of stars to form in the galaxy and very little was avaliable for the second set. There are a fair number of stars left over from this era, though they are mostly smallish. None of them were good places for life to develop and the few that did get lifeforms circling them never developd technological socities. On the other hand, those second generation stars did have at least a small chance of having a planet capable of supporting technological civilizations, though they were still metal poor worlds. On the other hand, even a small poor world has a lot of metal in it. The second generation of stars began to form about a billion years after the galaxy started condensing, though they didn't really start lighting up in large numbers for several billion years after that. But with the formation of a few star systems with more interesting elements than mere hydrogen and helium, you got the potential for life and thus sentient life.
The first races to reach out into the cosmos found themselves mostly alone. The first races to start moving around through it were able to spread out for quite a long while before they ever found any planets with life, much less other intelligent beings. This lead to the creation of massive star-spanning empires. Fortunately for us and all of the other species that popped up around third generation stars, most of the early races eventually signed a treaty that forbade them to settle planets with indigenous life. By that point in time a few hundred million ecospheres had been terminally disrupted, and not every race agreed to the treaty, but at least it offered potentially developing races a chance to evolve.
The galaxy was a relitively peaceful place for the next billion or so years. Even if you have the time and energy to travel between the stars, if you are doing it at sublight speeds you aren't going to be doing a lot fo fighting. A dozen sublight empires arose and settled the dead worlds of the galaxy. Even if you were the ultimate xenophobe, there wasn't a lot you could realistically do about it over those distances. Five billion years after our galaxy accreated, that was the state of reality. Over the next four billion years various sentient races evolved on the protected worlds within the domains of the various galactic empires.
Only two of the origional races are known today, both extinct. The Aldoni speak of two of the founder races, though they name them only "The Creators" and "The Nemesis." About a billion years ago, the creators designed the Aldoni as a servant race. They were created from the ground up, not based on any other biological system in the galaxy, with none of the evolutionary baggage inherent in coming from a cell line that has spent the last three billion years being the baddest badasses on the planet. Their instincts and urges are all aimed at their roles of overseers and guides to emerging races throughout the cosmos. They are also superb diplomats.
Well, about six hundred million years ago, one of the younger races with a (relatively) bizarre psychology proved the wisdom of allowing other races to develop undisturbed. They developed stone tools and then metalworking, pottery and cities. They had an industrial revolution, though their chemistry rushed ahead of their physics, biology, metallurgy, and engineering. They struggled to reach the space age, made the jump to another star system and were inducted into galactic society. And were given access to the learnings of the Creators. Well a thousand years later they came up for breath and with their unusual thought methods came up with something spectacularly new. They invented the hyperdrive. Within ten thousand years, everyone had them. Within a million, there was a galactic war. By the end of the war, there were two empires, the Nemesis and the Creators. A few of the Aldoni were sent away to a small star cluster beyond the edge of the galaxy. The Nemesis created their own warrior races (of which the Horde was one) while the Creators tried to stop them. As the fight went on, the outer worlds were systematically destroyed if they had sentient beings. The Creators despaired and created a permanent 30,000 light year sphere hyperspace deadzone that included all of their worlds as well as all of the Nemisis worlds. Then they started blowing up stars. In the end they were all dead and the Aldoni came back to a silent galaxy.

I'll give more background later.