The Y'Deio system is a planetary system centred around an orange dwarf star located 41 light-years from Earth and the Sol system, within former Covenant territory. It is the only known alien planetary system discovered centuries ago by humanity, and is referred to in human astronomy as HD 69830.
Y'Deio's planetary system consists of at least three planets and an abnormally dense asteroid field. The Kig-Yar homeworld of Eayn orbits the third planet, Chu'ot, a gas giant. Further out is an asteroid belt, with a number of Kig-Yar colonies built on small planetoids and asteroids, including Dal'koth. The numerous asteroid and planetary colonies of Eayn in the system are independently governed. One third of all Kig-Yar live on Eayn in the Y'Deio system, with the rest living on the system's colonies, primarily Muloqt, Kaelarot, and Valyanop.
The Kig-Yar race evolved on Eayn, the primary natural satellite of Chu'ot—a gas giant in the system. At some point in the Kig-Yar's history, the clans of Eayn united, and the Kig-Yar species worked together in developing space-travel technology. Shortly afterwards, they established colonies on many small asteroids and planetoids around Chu'ot in the system. Some individuals continued their ancient ways of life and became pirates, preying upon merchant starships. Many pirates operated in "kill-squads" that raided territories and colonies throughout the Y'Deio system. The influx of piracy in the system led to the Eayn government, and other colonial administrations, organized a militia to help battle the pirates.
In 1342, the Covenant arrived in the Y'Deio system with small contingent fleets. The Kig-Yar pirates and militia joined forces in an attempt to fend off the alien intruders. These fleets were directly attacked by ruthless Kig-Yar pirates and mercenaries, leading to a long naval war in the system. Despite the overwhelming force that was the Covenant military, the Kig-Yar used their home system to their advantage. The extremely dense asteroid belt that orbited Y'Deio made it difficult for larger Covenant vessels to navigate around Chu'ot, while the Kig-Yar used the asteroids as refugees. The war between the Covenant and Kig-Yar forces culminated in sieges of redoubts on the asteroid colonies surrounding their world. Eventually, realizing the unlikelihood of them winning the war and the opportunity to profit from the expansion of trade, the Kig-Yar joined the Covenant to serve as an essentially independent entity that operated as mercenaries for the empire.
Following the Human-Covenant War and the dissolution of the Covenant, many Kig-Yar returned to the Y'Deio system. The population of Eayn continued to grow within reasonable governing measures, while the system's colonies maintained a very stable economy.
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