The background story of the Followers of the Eternal Siren is the tragic story of the 3. Ragheln mixed guard regiment and of the return to power of one of Slaaneshs once most favored Keeper of Secrets.
The Bloody Rose, the Eternal Siren, the Voice of Weeping Death one of Slaaneshs Keeper of Secrets has been imprisoned for thousands of years on the world of Sicar IV. But after her long imprisonment the sacred chambers that bound her powers started to give. Her fleeting presence was still weak but over the year it sparked the flame of rebellion against the Imperium of Man. The ensuing yearlong civil war was the reason dispatching a mixture of different guard regiments to the war-torn world. The 3. Ragheln – a mostly unknown backwater-world regiment of mixed gender – was one of them. While the war above the prison of The Eternal Siren turned into a stagnating trench warfare the death cries of the dying soldiers weakened her bonds even further.
After years of eventless conflict many events occurred at nearly the same time and exploded into a chaotic chain of events that ultimately molded the first of the Follower of The Ethernal Siren.
One event was the dispatching of a small force of Grey Knights. They had learned of the Eternal Siren and her weakening imprisonment. They advanced towards Sicar IV to encounter the jailed demon in her current weakened state and rebound her into the holy prisons of the grey knights. They didn't expect a strong foe so they dispatched only a small force. But the deadly trained warrior where still a strong force to reckon with.
At the time of the grey knights arrival on the war-torn world the next event started. The rebellious forces made an advance on all frontiers -their last effort to either win the war or die trying. This move came totally unexpected and many frontiers where overrun. The order was given to retreat to the second line of defence and hold the assault there. The 3. Ragheln where trapped directly in the middle of the advance. The allied regiments around them retreated to hasty and the rebels where able to surround them. The rag tag backwater regiment had been a thorn the side of the royal regiments fighting next. So they decided to abandon their allies and shell the former defence line with massive artillery fire.
Surrounded by enemy and shelled by their own blue-blooded allies the next event occurred. Misfiring artillery blasted open the hidden entrance to the prison of The Elternal Siren. With nowhere else to go the 3. Ragheln entered the dark halls of the prison to get at least protection from the exploding shells. With hate for their allies anger and fear in their heart is was no wonder that even the weakened Keeper of Secret could lour the guardsmen and -women towards her prison. She strengthened those easy to influence. Imbued with the warp-spawned power the Ragheln fought off the rebels. But in the same moment the last rebellious soldier hit the floor the Grey Knights teleported in.
They Grey Knights quickly realised what had transpired. They could feel the warp influence on the guards. But the stronger minded soldiers also started to see the changes in their comrades and pulled their guns at them. While the Regiment started to fight against their tainted comrades the Grey knights made their devastating move. All of the men and women had been bathed in the power of the Keeper of Secrets. The Grey Knights couldn't risk anyone influenced by the power of the warp escaping. So they opened fire on all of them.
Those guardsmen who hadn't jet realised what was going on where shocked to see their glorified allies - the gods of the battlefield the astartes where for them - to turn their fury on them. Some opened fire on the holy warriors.
In the midst of all the chaotic carnage The Eternal Siren called the 50 strongest under her influence towards a hidden armory. There they found wargear of the former guardians of this prison. What had happened with those long since forgotten warriors was unknown. But they had left their power armor and weapons behind. Bathed over thousands of years in the presence of The Eternal Siren those armors and weapons where filled with corruption and power. The 50 soldiers donning the possessed wargear where infused with mind and body warping forces. Bodys grew and muscles bulged and their frame changed into the image of the Elternal Siren. They now filled out the armor like the astartes who had worn these armor once.
The appearance of 50 fully armored and armed warriors took everyone by surprise. But the Grey Knights didn't falter and fired at the powerful jet untrained possessed soldiers. But amidst all the death and carnage the holy warrior realised to late that every dying soul, every last breath strengthened the trapped Keeper of Secrets. With a burst of shards the spinning orb holding her imprisoned burst open. The newly empowered demoness slammed into the Grey Knights. Channeling part of her powers into the possessed 3. Ragheln guardsmen and women the holy warrior where assaulted from multiple sides. Lasgunfire from the confused guards. boltershorts from her chosen and the sense-shattering voice of The Eternal Siren overwhelmed the holy warriors.
After the bloody battle those who pledged alliance with the freed demon where spared. The strongest under them where given the armor of the killed possessed refilling the 50 warriors.
Those who didn't side with the angered demoness where gunned down and their blood splattered all over the armor of the fallen Grey Knight. The desecrated warriors where left behind.
The imperial guards outside had been informed of allied astartes on the battlefield. So they where taken by surprise as the power armored warriors walking towards them suddenly opened fire. With the Elternal Sirin in their midst the survivors advanced through the gaps the hasty repositioning of the regiments had created. They captured a landing vessel and in a short and bloody massacre a ship capable of warpflight.
In their search for a new place of power the Follower of The Eternal Siren found the location of a circle of Tzeenchian Sorcerers. They had been working on a way of corrupting and multiplying the genseed of loyal chapters to recreate a method of replenishing the forces of the chaos marines. The only thing they needed was immense additional power the demoness was ready to give. But she had a hidden plan. She knew that the Grey Knights where still on her heels. She had even left behind a followable trace on purpose. As the Grey Knight ship appeared in the system she used the confusion of the preparation for battle to load a large chunk of the heavy wargear and chaos vehicles into the stealthiest spacecraft docked on the base. The strategically placed Followers of The Eternal Siren dispatched everyone on the ship who would oppose her leadership quickly. While the holy warriors stormed onto the moonbase full force a single craft slipped away under the radar – belly full of tanks, transports, heavy cannons and weaponry and a few sorcerer and chaos marines that pledged alliance to The Eternal Siren. But the most important stolen equipment was the machines and knowledge the demoness had helped to create. She now possessed the maschines to create chaos astartes out of captured geneseed. This would allow the Followers to create new warriors without knowledge of the special ceremonies some of the different chapters genseed required to activate. And the best was that they had erased all evidence of what had transpired in there research before departure. The Grey Knights would gun down every other Tzeentch follower who had knowledge of the infernal machinery. The only trace they had left behind was the feeling of defeat in the eyes of the Grey Knights who had lost all traces to follow the empowered Keeper of Secrets. With the moonbase blown into oblivion the only left behind traces were the bloodstained armor of the Grey Knights killed on Sicar IV and the reports that had let them there to begin with.
With the power of the Elternal Siren and the ability to replenish their troops it was an easy task to silently take over a world on the outer rim of imperial space. There The Elternal Siren now residues in her walking temple her trusted Followers at her side.