Xyon

Xyon is a dry and arid world located in the Ultima Segmentum just north of the Galactic Core. It is unique in the fact that it is home to a race of Sanctioned Xenos known as the Xyonians that live side-by-side with Human settlers. The Xyonians are a humanoid psychic Xenos race nearly physically identical to Humans and have the ability to scry future events. The presence of Xenos, sanctioned or not, has lead to Xyon being isolated from the rest of the Imperium.

Xyon is also home to the Temporal Lords Chapter of Space Marines. The Temporal Lords are known for having a variety of gene-seed flaws ranging from potent psyker abilities as well as the ability to scry future events (similar to the native Xyonians).

History
Xyon is an ancient world that is possibly one of the first planets in the Galaxy. The native Xyonians are equally ancient, being one of the oldest Humanoid races in existence.

The early history of Xyon has long ago been lost. The oldest reliable records date back 3.5 Billion years ago and involve a technological and political revolution that overthrew the planet's superstitious theocratic government and replaced it with one based on democracy and scientific advancement. Even after annexation by the Imperium, the Xyonian government has gone largely unchanged over the last 3.5 Billion years.

Great Crusade
The Xyonians have largely remained isolated and content to keep to themselves. This changed when they were met with the forces of the Great Crusade lead by the Emperor himself. After a relatively brief battle the Xyonians surrendered before the Emperor. Strangely, instead of annihilating the Xenos, the Emperor gave them "Sanctioned" status with very limited planetary autonomy. This was likely because the Emperor saw that the Xyonians "temporal awareness" would make a valuable resource for the Imperium.

Despite the Emperor's previous proclamation he would later order the systematic genocide of 10% of Xyon's Xenos population

Desolation of Xyon
In the final days of the 41st Millennium, the planet Xyon was faced with the greatest assault in it's history since the Emperor's 'Cleansing of Xyon' in the Great Crusade.

Various Marines of the Temporal Lords had been receiving prophetic visions of the desolation of their homeworld a thousand years before it occured. This allowed the Temporal Lords to convert their homeworld into a mighty stronghold before the impending doom. Massive fortresses were constructed, large defense systems were put together, and the Xyonian looms (an esoteric method of artificially producing offspring) were pushed to maximum capacity.

The belligerent, militaristic and cybernetic Xenos race known as the Skaevos invaded the planet Xyon full-force. The Skaevos Military met resistance of the complete Temporal Lords Chapter, the Xyon Castellans (Sanctioned Xenos Military), and the Xyon PDF.

As the battle began the Cicatrix Maledictum split the Galaxy. The formation of the 'Great Rift' lead to the Xyon System to become encased within an impassible Warp Storm.

The Temporal Lords, the native Xyonians, and the Humans stood united against the Skaevos Empire end eventually drove the Skaevos to extinction (having deployed their entire race). Despite their victory, 90% of the 9 billion inhabitants of Xyon had been killed and the Temporal Lord Chapter was nearly eradicated. The entirety of the 4th, 5th, and 6th Company being wiped out (however, the 4th Company was not destroyed, rather it was lost in the Warp Storm whilst engaging the Skaevos Naval forces). Only forty-five Veterans, eighty-three 2nd Company Marines, and fifty-two 3rd Company Marines remained. This left only 180 Marines to carry on the legacy of the Temporal Lords Chapter. It was only through their millennium of preparation were the Temporal Lords able to save Xyon from complete obliteration.

When the Warp Storm around the Xyon System finally dissipated, the shattered Imperials on Xyon were met with forces of the Indomitus Crusade. It was then that they discovered that while they had spent 540 years battling the Skaevos, only a few months had passed for Terra.

Geography
A dry world, Xyon is covered mostly by burnt-red deserts with orange sand and seemingly endless mountain ranges. Red grass fields strewn with rubble as well as forests of silver-leaved trees are also present, but they make up the minority of the terrain.