Gudan Prime

Gudan Prime is a notable hive world of the Gudan System, located in the Segmentum Ultima. This planet is also the Adeptus Astartes Chapter home world of the Bulls of Retribution Space Marine Chapter, that stands as the system's stalwart guardians against the various enemies of Mankind.

Background
The Gudan System was first discovered by the Imperial Fists Legion in the early years of M31, during the dark times of the Horus Heresy. If local legends are to be believed, it is said that the Imperial Fists fought the Traitor Legion of the Night Lords, and the fighting was brutal in the extreme. Many worlds throughout the sector were put to the torch, and untold billions slaughtered in the name of the Dark Gods. When the Imperial Fists attempted to respond to a traitor invasion of Gudan Prime, they found upon planetfall that they were not the only humans fighting to defend the populace of that world.

The group known as the 'Horns of Gudan', though only a loose coalition of tribes and hive gangs, had risen in force against the traitor invaders, casting aside their petty gang wars and turf disputes to instead rally against the warp horrors that encroached upon their home. So successful was this defensive action that the Night Lords had been unable to breach the inner defences of the capital hive, Hive Vaxilian, and the vast majority of the populace there had been saved from fates worse than death.

The Sons of Dorn held these humans in high regard, for they'd fought against Heretic Astartes of the Ruinous Powers with nothing more than blood, autoguns, and steel, and against all the odds had succeeded. Following the war, the Imperial Fists made Gudan a recruiting world, building a Chapter Keep at the pinnacle of the highest spire of the planets greatest hive city; Hive Vaxilian.

However, it would not be until M32 that an Imperial ship, the Inquisition vessel Gallow-Tree, returned to the Gudan System. Despite the apparent daemonic nature of the Gudan Star, the central sun of the Gudan System, the Inquisition realised the worlds in orbit of the strange star existed without mutation or deviancy. Another aiding factor to such colonisation was revealed when auspex scans uncovered the ruins of human structures from the Dark Age of Technology upon the surface of Gudan Prime, a planet within the star's goldilocks zone, and that a viable human population had existed there for over six thousand years of isolation without major deviancy from baseline humanity.

So it was that in M33 an Imperial Crusade was launched to establish the Gudan Sector, with the Gudan System, and star, at its very heart, shielded from traitor influence by whole star-systems dedicated to its defence. Though the fact that the sector existed solely to protect a daemonic star was known to only a handful within the Ordo Malleus and the planetary governor of Gudan Prime, the sector flourished, and for five thousand years was a bastion of loyalty and faith on the further edges of the Ultima Segmentum, guarding the emperors domain against those horrors from beyond his light. The centuries slipped by, and as all things are, the exact nature of the creature that slumbered within the Gudan star was lost to history, known only to those scribes charged with keeping the records in the vast vaults of Terra. Only the Imperial Fists truly remembered what had occurred in high orbit above the star, and the name Writhing Wyrm.

By 564.M38 the region had become stabilised enough that the High Lords of Terra deemed a new Founding was required to defend the burgeoning sector, and Imperial Fists knew just the world, and just the gang, suitable for the task. Thus, the Bulls of Retribution Chapter was born. They have stood as the Gudan Systems eternal sentinels since their inception, protecting the various worlds of the system from any threats that would dare assail the worlds of Mankind.