The Diseased Sons are a chapter of space marines that have fallen to Nurgle, the chaos god of disease and decay. Although they are not one of the original chapters that turned to chaos during the Heresy there are none more devoted to father Nurgle. The Death Guard are first among Nurgle's chapters and are like a big brother to the Diseased Sons. There is a sibling rivalry but no real hatred. All of Nurgle's followers are one great big happy family with Nurgle there loving, doting father. His generosity has turned members of the chapter into bloated, rotting, diseased stricken, walking monstrosities, but they accept his gifts as family traits much like hair or eye color is passed on from parent to offspring.
Overall they are content in their service to the Dark Gods unlike many of the other chaos chapters. The Diseased Sons are not filled with rage and hatred like the Worldeaters or the Black Legion, nor are they somber, dark, and brooding like the Night Lords. Do not mistake their apparent good nature for weakness, they fight with a fierceness that has earned them the grudging respect of the other chapters that dwell in the Eye of Terror.
Nurgle unlike the other three great chaos gods has his power ebb and flow with the tides of death, disease, and corruption. It was at a particularly high tide, when war and death were rampant along the Eastern fringe of the Empire of Man. Diseases were running roughshod inside the great Hive Cities of Necromunda. And corruption had slithered it's tentacles up to the highest rungs of command in the Empire, to the Lords of Terra themselves. It was in these turbulent times when the Diseased Sons came to be.
The Lords of Terra had degreed that another founding of Marines was to be created to raise more troops to fight the vast Ork Waaargh led by the infamous Ork Warboss Mikka Waa-Dakka-Dakka-Dakka Raataafada that was pillaging and looting Imperial worlds all over the Eastern side of the Empire. And so the founding was ordered, gene seed was prepared, applicants were chosen from amongst the finest Imperial Guard Regiments the 5th Tallaran, the 12th Mordian Iron Guard, the 3rd Armagedonian, the 1st Cambodian, the 13th Mofo's of Cowichan, as well as the Spyders of Necromunda. The last choice was to be one that the Lords of Terra soon would come to regret.
All the necessities required for founding a Chapter were commissioned and assembled on the Imperial world of Victoria. This was to be the training ground for the new chapters, of this, the 13th founding. The Tech-priests of Mars had turned out the masses of power armor, bolters, and tanks that would make up the battle armament of the new Chapters. Gene seed had been acquired from a wide variety of Chapters known for the purity of their gene seed. Various Imperial officials were present along with the thousands of applicants. All was in readiness for the creation of the new Chapters.
This founding started out very auspiciously. Very little gene seed was rejected, most of the applicants survived, and very few abominations were reported. The Ordo Mallus was on hand as always watching for the taint of Chaos. All was going well, the surviving guardsmen from the various regiments were divided into 10 new Chapters. These were not full Chapters yet. They were not 1000 strong but rather would grow to that size or larger over a number of years. But first there was training to be done and additional observation was warranted to ensure that these new Chapters were free from genetic defects.
Supervising the training was a Captain and an entire company of the Empire's finest soldiers the Ultramarines. Who better to instruct these new marines on the Codex Astartes then the Ultras? As an additional precaution a Gothic Size war barge of the Imperial Fleet was in orbit around Victoria.
For months things were continuing to go well. The gene seed continued to appear pure, the Ordo Mallus believed these the newest space marines were free from the taint of chaos, and very few had died as a result of training accidents. A high ranking Imperial official was sent forth by the Lords of Terra to officially create the new Chapters. This involves naming the Chapters assigning them colors and insignia as well as a home world.
Up until now they had been training in bare metal armor or at best a coat of white, black, or gray primer. This was to remind the new applicants that they were not full marines yet like the Ultras resplendent in their bright blue power armor. The shame of being all metal or at best primered was to remind the applicants that they were not yet the Emperor's finest warriors, merely aspirants to that loftiest of titles.
The official names and colors of these the Chapters of the 13th founding is stricken from Imperial record. Only those in the highest Imperial offices on Terra and some high ranking Inquisitors know that some of these marines survive to this day, albeit in a hardly recognisable form. Shortly after the official ceremony and the reissuing of painted armor, tanks, speeders and bikes. These new chapters had no dreadnoughts as they had no fatally wounded heroes yet to entomb. They also had no Terminator armor this being, so rare and valuable, it was only issued to veteran marines. These chapters being newly created had yet to see the field of battle and as such had no veterans. Most of the Imperial officials went home after the ceremony was completed. The Ultras returned to their home world after successfully forging the ex-guardsmen into humanities finest warriors. The Gothic war barge was gone replaced by a fleet of transports to take the Marines to their new home worlds, which were currently occupied by orks.
The marines were to be shipped to the Eastern side of the Empire to fight under the veteran leadership of the White Scars and Imperial Fists. This was standard Imperial practice, the new legions had no officers such as Captains only sergeants. They also had no Chaplains, Tech Priests or Librarians these specialist marines required extra training. They would be chosen from the ranks of the new chapters at a later date. But first the Empire needed more troops to fight the hordes and hordes of orks overrunning the Eastern side of the Empire of Man. The basic marines were trained and formed into standard assault, tactical, and devastator squads. They had vehicles but lacked the expertise to maintain them. The Ordo Mallus had also departed, for who is more free of the taint of chaos then humanities finest warriors?
Just before the new marines were set to depart, many of them became deathly ill. The disease struck with unbelievable quickness. A marine would be healthy and normal one day, the next they would be covered in dark purple welts and too weak to stand. This calamity struck roughly twenty percent of the new marines. However it was not confined to one particular chapter or even one particular line of gene seed. Imperial officials were puzzled and held the marines on Victoria for further observations.
If the Imperial officials had bothered to check which guard regiment they had come from rather then which chapter the gene seed had come from maybe they would have taken quicker action. Perhaps if the Inquisitors hadn't all departed they might have recognised the obvious connections to the Chaos god Nurgle. Perhaps if some military men were left in charge such as the captain of the Ultramarines instead of some corrupt bureaucrat more decisive decisions would have been made and this tragedy could have been adverted. As it was the officials in charge chose to do nothing except wait. The infected marines were all quarantined off by themselves on the West side of the vast city complex that had been constructed specifically to create, train, and house the 13th founding. This would be another decision Imperial officials would come to regret when the Inquisition made their report.
The West side was the farthest possible distance from the barracks where the healthy marines were quartered. The official in charge reasoned that this was safest for the other marines as they did not want more battle brothers catching the illness. Losing twenty percent of the newest marine chapters would be looked on with enough harshness by his superiors back on Terra. No sense endangering the rest of them needlessly. So it was for many days, the sick remained sick, the uninfected marines remained cooped up in their barracks for observation. Since the marines had not died the official in charge had hoped they might yet recover. And when some of them started to stir from their sleeping platforms he became down right giddy. It was only when they busted out of their quarantined area and headed for the armoury which was thoughtlessly close to the quarantined marines did he get a sinking feeling in his stomach.
The alarm was sounded and the pure marines were sent forth to stop them. Contrary to popular belief marines don't sleep with their bolters, and much of the chapters armaments were being stored in the armoury prior to the chapters departure for the Eastern fringe of the Empire. So even though they out numbered the diseased marines four to one they were seriously out gunned. To make matters worse the diseased marines had fortified themselves securely in the armoury. But to their credit the new chapters fought with a fury and determination worthy of any of the more established chapters. Some marines bereft of their power armor and armed with only a bolt pistol charged the fortified gun emplacements of the diseased marines. Just when it looked like the pure marines were going to prevail, having broken through the perimeter.
Scores of demonic followers of Nurgle descended onto the battlefield. Reams of Plaguebearers tore into the pure marines cutting them down with their plague swords. Waves of Nurglings swarmed over the astonished loyalists, overwhelming them with sheer numbers. Throughout the battlefield Plague Beasts of Nurgle were cheerfully playing with one victim after another. And towering over all were the Great Unclean Ones in the likeness of Father Nurgle himself. They could be seen cheering on the others like a loving parent. Yelling out helpful suggestions like "Stab him good Pussmonger" or "Don't worry Sluggie you'll find another playmate."
In a short time the entire population of the city were dead, dying, or happily infected with a number of diseases. The fleet was in a similar state as it to was also overrun with daemons. Some ships escaped and many warnings and cries for help were sent out. But Nurgle didn't care, he had his prize the newest marines were now his. The marines who had taken to calling themselves the Diseased Sons to honor their true father, gathered up their equipment boarded the remains of the fleet and made haste to the Eye of Terror.
The official report, by the Inquisition, determined the cause of the infection, to be a more powerful, but dormant form of the disease that was currently sweeping the Hive Cities of Necromunda. The Ordo Mallus gained new found respect for Nurgle, previously they had always thought he was the weakest and most simple minded of the major Chaos powers. But to hide something of this magnitude from the Inquisitors present, and to only reveal his hand after the Ultras, the Inquisition and the Battle barge had left was a scheme worthy of Tzeentch. Nurgle had dealt the Empire a major blow, not only did he destroy years worth of effort to create another founding. He robbed the Eastern side of the Empire of what would have matured to ten chapters of space marines to help them fight the Waaarrgh that was rampaging within it's borders. But most damning of all, Nurgle added yet another Chapter to the list of those who had fallen to chaos.