100th Millennium Wiki
100th Millennium Wiki

The Ysau are a species native to the planet Ysi in the Ouranir Galaxy. The species can be found in many places throughout the universe, but the majority live in the Ouranir Galaxy, with smaller populations in the Ventemir Galaxy and Via Sagittaria. The Ysau are carbon-based bipedal humanoids that posses no clear head. Instead, they have eye-stalks atop their "shoulders." They posses vestigial claws that evolved to use tools rather than be weapons themselves. Ysi has fairly low gravity for a Terra, making the Ysau quite tall at two meters on average.


The Ysi are fairly typical in terms of biology. Ysi bared the most common form of life, carbon-based and oxygen-breathing lifeforms that reproduce sexually. The Ysau hatch from eggs and start out only about ten centimeters in length in a larval stage. From there, they remain helpless for two years while developing muscles, brain material, and fat reserves for their metamorphosis. After they weigh about 30 kilograms, they will wrap themselves in a chrysalis and transition into maturity. After several months of complete dissolution in the chrysalis, they will emerge fully sapient, capable of walking, and capable of learning. From there they will take another ten years to reach full maturity both physically and mentally.

The Ysi contain both an endo and exoskeleton. Over their torso and fore arms, there exists a thick layer of chitin meant to protect the individual from attacks. On the rest of the body, to facilitate mobility, there are internal bones surrounded in muscle and then skin.

The brain is located with the rest of the organs in the torso and is relatively large but decentralized. Sensory information comes from a variety of places across the body. In the eye-stocks, there are smaller "sub-brains" that preemptively process information before sending it to the main brain. These sub-brains mostly remove noise from the input to save time in the main brain.

Rather than distinct ear drums, the Ysau detect vibrations through whatever part of them (not covered in exoskeleton) is directly touching the ground. This is usually through their legs. The eyes atop the eye-stocks are capable of rudimentary sound-detection, however, the three hundred and sixty degree vision of the Ysi have mostly negated the need for auditory perception.

Over half of Ysi's, atmosphere, is made up of water vapor, warranting the need to process it. Their lungs filter out most of the substance, however their lungs can also feed some of this vapor into a specialized organ. Roughly translated from Ysau, it is the Condayrar. When in need of water, this organ, situated at the back of the lungs, will pressurize water to the point of condensing into a liquid. From there it can be used in the Ysau's body. The Ysau also possess a large storage bladder for water that can hold enough liquid to allow the individual to go months to years even in the dry conditions of Ysi's winters.


The Ysau first emerged as small groups of hunter gatherers, using the sharp points of their claws to tear into the tough husks of fruits or to tear into prey. After over one million years, they began to develop tool-use. This gave the Ysau incredible advantages such as fire and basic spears. By 10,000 BC, the first Ysau cities had begun to form. They subsisted off domesticated animals and tightly packed groves of fruit-bearing trees. Not long after this point the first kingdoms arose and began to war with one another. For about 4000 years the Ysau were divided, warring with each other just as most primitive sapient species do.

Around 0 CE, the Ysau attained space flight, and set up colonies only a century later. They would eventually form a nation known as the Interstellar Systems of Ysau. The nation remained relatively minor until the fall of The Triumvirate Civilization in 1,870 CE, when it was finally free to expand across the Ouranir Galaxy. The Ysau would expand with it and become the most common species in the galaxy.

They would later be forced to join first the Yohjan Confederacy and, later, the United Federation of Star Systems. To this day they are still technically living under the UFSS in a protectorate bearing the same name as their original nation. This, however, was accompanied by great improvements to average quality of life, so most Ysau do not even desire independence.