Hmmm... I don't really think that middle ages would be a fit for the Zaahir(plus there already is a medieval race-the glitch) Perhaps some kind of bronze to iron age society and tech-level would fit them better, and if not that, then perhaps a 19th century ottoman empire-esque societyy would be good. I think that it would be cool if the Zaahir were a mining race(boring beetles), and the way that they achieved FTL speed(and make their weapons equivalent in power those of the other races) was with a special (possibly radioactive) fluid found in the depths of their planet. This fluid would be infused with metal weapons to greatly increase their power, and allows them to achieve interstellar jumps by coating their ships with it. Perhaps they evolved to produce it(so the character wouldn't need to gather it to make weapons) as a defense mechanism(since the substance is extremely dangerous and they can secrete or spray it).