Worldcraft Contest: Demdae

This civlization was created for the Worldcraft contest #5. I planned a basic redesign of the 'pitch black' creatures but I quickly realized I was developing something to different to be that. Had several ideas and this one came to be the best.

"The demdae (or demdaea, for plural use) civilization developed near the end of the stelliferous (star-filled) universe. As the cosmos is more abundant in heavier atoms, their's is a boron-based biology. They evolved form tetralaterally-symetrical creatures with powerful tails on top of their bodies. Demdaea are now tripedal beings with two forelegs and a supportive hindleg derived of their tails. The two remaining appendages have become sensory/manipulative extrematies. The lower arm was a display organ with rpid movements. The upper arm was equipped with four digits, a central ganglia, and display wattles and membranic photoreceptors. There is a second ganglia within the dorsal plates of their skeleton, between their forelegs. This gives them a sort of 'two-faced' personality; a basic set of primal urges, and a higher consciousness of more developed ethics. These two minds intimatly overlap eachother in society.
Demdaea developed a highy advanced civilization within their home system. They never expanded any further, since stars were an increasingly rare sight in their age. After mellenia of peaceful development, their society drifted into isolationism, distrust, ethical breakups, economic fall, and eventually massive civil war. One population on a teraformed world was marooned without ships and forced into hiding. They excavated enormous caverns sheilded from scanning radiation. In this act, thy unknowingly created an ark of sorts for what would become the last remnants of their kind. Enemy factions disrupted their star, making it more unstable with frequent blasts of heat and radiation. Others moved the ark-world closer to the star in hopes of roasting off any survivors. But the now-violent star and crippling wars doomed all other demdae cultures in the system. It is believed a genetically-enhanced super-virus was the final blow to the other demdaea. The survivors of the ark-world developed into a newly stable society within their artificial caves. Their world had been robbed of most metals, so mining is of primary consequence. They have had to adapt themselves to their dark home. The lower arm, once a rapid visual display, is now a long whip-like antenae for feeling around. Their photoreceptors, derived from digits, have been modified into echolocator-organs. Their four manipulative digits now posess carapeice-like pads at the fingertips to enhance their snapping ability, which is now their main method of communiation.
The elite classes of demdae society had recently established the first permanent domed settlements on the scorched surface in several centeries when the nexus opened, freeing them to explore the universe.