An empire starts one-species, but then new ones may join it through conquest, merging, or immigration. A person may be of one species. The descriptions are procedurally generated, following a few patterns, "human", which is a fixed description of, well, a human, "almost human", which is human with some variations, like weird skin colors or additional or missing bodyparts, "humanoid", which is, well, broadly humanoid, "quadruped", which is exactly what it says on the tin, and "weird", which can get weird, like octopuses with 60 tentacles that smell color. Each species has a few traits, which can be positive or negative, like increased fire rate for ships that species is the captain of, more wealth generated from a stellar governor, or on the negative side, making stupid decisions or screwing up diplomacy or making ships randomly explode. These traits are liked to the description. What do you think?