Humanoid in appearance but thinner, they have aspects of scorpions. Their heads resemble those of terrestrial skeletons. They have six arms, the lower four being smaller and having four digits with which they use to manipulate smaller tools and for anything that needs refined work. The upper two are twice as long and have only three digits. They use these in wars for battle or for heavier manual labor. Their feet have three large digits and they also have a tail similar to those of Earth scorpions.
All over their bodies there are certain parts that are covered with spikes like those on a porcupine that are filled with a venom that can kill anything unlucky enough to touch it. They are located on the back of their legs, back of their upper arms and above their two eyes where eyelashes would be. They have a lifespan of 250 terrestrial years.
The Un’rin evolved on their moon 1.2 million years ago, emerging from an ancient sea during a part of their history where their atmosphere was thicker and warmer, allowing temporaty liquid seas to form on the surface. As the atmosphere shrunk and the water sublimed, the proto-UIN’rin evolved thicker carapaces as well as poison sacs and the ability to hold water in their bodies for much longer.
Their first few thousand years were spent scattering across the planet from their original home sea, a hunter gatherer society. Eventually some 300,000 years ago many of the larger groups came together near their ever dwindling sea and formed a small civilization, discovering many basices of society, agriculture, government etc. Many of the other hunter gatherer societies, wishing to emulate this new idea, formed smaller communities nearby. Eventually they became one massive civilization, highly developed, a bit more advanced than the Roman civilization in its prime on Earth.
However the dwindling water supply and older temperatures caused this great civilization to crumble to wars and inner political conflicts. The people spread apart and formed smaller civilizations for thousands of years until they once more came together near the ruins of that first great civilization and forged a new alliance, forming their caste system which has kept their society going to this day.
They grew in numbers and technology and eventually reached to the stars some 750 years ago, landing on their neighbor world and discovering an ecosystem so alien to them it took them centuries to completely understand it. They began to dabble in bioengineering themselves to be able to live on this new world and to experiment with terraforming. 240 years ago they settled on their neighboring world and formed a colony with their new caste. There they also discovered the Riyn, large lumbering silicon based lifeforms that they could engineer to become the perfect slave labor on both their worlds.
They visited their neighboring world of Cervan 130 years ago and discovered the Cervantes as well as a world full of life and water. However, they decided to mine water from the moons of one of the gas giants in the system for their needs, forming a very thin ice ring around their homeworld and colony worlds.
As of their discovery they have not yet achieved FTL but are beginning to work on it.
The current Un’rin culture is a heavily caste based system. The highest castes are the leaders, a high council, each member a former member of one of the higher castes. There are other castes such as science caste, farmer caste, lawmaker caste, and other smaller castes. With the recent addition of the slave and colony castes a new seat for the colony castes has been added but the seat for the slave caste wasn't added.
Each caste is dependent on the other in order for their society to survive. Each caste has certain benefits that the other castes do not share.