The Endless Blue
The Orcs stand at the head of a rigidly structured society built around one purpose: to conquer and consume everything in their path. Generations of controlled breeding and interspecies hybridization with enslaved races have left most orcs as towering specimens of physical perfection and strength. Their technology and magic is unstable but powerful; their ships are very radioactive in a number of ways, so their warriors fight all the more savagely because they know they’re going to have short lives anyways. By that same measure, soldiers and officers are rendered sterile by serving on a ship, so genetic samples are harvested beforehand, and those who prove themselves in battle have the honor of their stock being used in the breeding pits.
A number of slave races have been forced into the ranks of the Legion. Crafty goblins are mostly responsible for maintaining Legion technology, and have brutishly short expected lifespans, whether at the hands of an unsatisfied overseer or the mercy of a malfunctioning engine; fortunately, they can also be bred quickly and in great numbers. The insectoid thri-kreen and savage shifters are treated like animals, kept on leashes and encouraged to bestial behavior, fed on the flesh of other sentient races. Massive ogres and hobgoblins are used as shock troops and pack animals. Other captured races, including unlucky humans, are used up quickly as slave labor and not considered worth including in their breeding programs.