how about this:
Race T is unique in the fact that it has a symbiotic relationship with something that is non-organic: each T is born missing certain vital biochemicals in its body required for sexual maturation. This is the result of tampering with certain chemical weapons in the race's past, resulting in a species-wide deficiency.
They counter this deficiency with injections of trace amounts of mineral U, which is found in abundance on their home planet (a careful consideration when terraforming: will the planet support mineral U?)
These trace minerals must be injected into the bone marrow as well as deep muscle. The effects aren't noticed until the race reaches adolescence, when the minerals emerge, first as bumps on the shoulders, spine or skull, but soon the mineral protrusions become apparent. Mineral U is a clear, quartz like substance, which provides enough essential minerals to last a Race T throughout their lifespans.
They're a race steeped in the idea of self-perfection, both physically and spiritually. To be a great male in T society is to speak many languages, be knowledgeable in all fields of science and arts, as well as to be a great warrior, and involved in courting mates. Feminine beauty is paramount for all T females, as well as knowing enough to carry conversation with a courting T male.
In dealings with other races, they will try and impress those that they believe to be their betters, or impose their authority to inspire the awe of their lowers.
Think if Renaissance values stuck with our society as a whole.