The Expletus Dissimul Insurrection

This is a story describing the invasion of the Emperor's Nightmare's homeworld of Icelus

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Mid-M40:A sect of the Alpha Legion known as the Flawed Ones, who had existed in the Veiled Region for many millennia, had begun expressing an interest in the actions of the Emperor’s Nightmare. They infiltrated Icelus, seeding their corrupted cultists among the hives and nomads over a generation. They watched the initiates of the Nightmare’s perform their trials, and slowly managed to sneak a few of their own into the ranks of the Nightmares, both through initiates raised from the bottom up, and by disguising Alpha Legion marines to pass as Nightmares via dark pacts and sorcery. They prided themselves on their ability to pass by the acute sensory perception of the Emperor’s Nightmare.

The Flawed Ones were biding their time, waiting to strike when one of their disguised marines happened to be in proximity of Brother Damien, a former Chaplain-turned Sleepless. Years of practice testing for purity and identifying taint, combined with a sense of perception magnitudes greater than his brothers allowed Brother Damien to detect the subtle imperfections of the imposter marine. Damien attacked the Alpha Legionnaire on sight, declaring him an imposter and a traitor. A fact that his fellow marines did not take to heart immediately due to his particularly severe loss of self. The imposter marine was rescued and allowed to go free, however Damien’s actions had spread to other Sleepless. He had brought to notice a crack in the imposter’s disguises, even those who had been brought up as initiates, which could be seen by other Sleepless. More and more Sleepless, particularly those who still retained some of their senses began attacking marines they could now see as imposters. They pleaded with their brothers to see what they saw, despite the imposter marines’ denial of having done anything wrong. Eventually, the matter was brought up to The Wake. It was then that the Flawed Ones had to act now or be completely revealed.

Before The Wake could make any decision, The Flawed Ones’ plan was set in motion. For years, Alpha Legionnaires had gone out into the Northern wastes, disguised as Nightmares and assaulted numerous Redemptionist tribes, including several that had grown quite passive over the years. Their nomad cultists whipped the tribes into a fervor for astartes blood. Meanwhile, cultists in all five hives had gained followers with varying degrees of success.

The plan began when The Flawed Ones’ two grand cruisers, the Pillar of Disgust and the Hashasin, exited warp and moved in to assault the Star of Dreams, who only had a small handful of fast attack vessels and a pair of strike cruisers to defend it.

On Icelus, The Flawed Ones threw off their disguises and began the assault on Betten-Burgen from the inside. Imposter marines who had been put into false sleep cycles awoke prematurely, murdering the chapter’s psyker aides. Four companies, plus most of the Night Owls and Scout Company were on Icelus and quickly moved to defend their home, the rumor of the Sleepless assaulting specific marines keeping the marines from being taken completely by surprise. However, they were unaware of the scale of infiltration the Flawed Ones had performed. Chief Librarian Satterthwaite, in addition to a quarter of the sleeping marines were already dead by the time help had arrived to the sleep chambers.

The fighting across the rest of Icelus was brutal. The Icelus PDF were put to the test defending key points of all five hives at once, as a massive mob of Redemptionist beat on the walls of Betten-Burgen and Hive Primus.

Many of the Sleepless, including a member of the Waking Dead were released to fight off the Flawed Ones from Betten-Burgen with great success and great collateral damage. In the end, Betten-Burgen was free of Alpha Legion imposters. But with messages streaming in from across Icelus of the cultist uprising, the marines were forced to divide themselves to lend aide. Thankfully, the highly trained PDF had managed to take control of Hives Secundus and Quintus, with Primus on the verge of being reclaimed.

In space, the Star of Dreams was taking heavy damage from the two grand cruisers. Two fast attack vessels had already been destroyed and a third was already being forced to limp away from the battle. With perfect coordination, the pair of strike cruisers were able to force the Hashasin out of position and surround it, using their combined arms and the guns of the Star of Dreams to hulk the chaos vessel. The Pillar of Disgust had closed with the Star of Dreams and begun boarding actions, forcing the marines and PDF on the station to fight against the Flawed Ones directly. One of the strike cruisers, the Endless Vigil, made a bold move of boarding the Pillar of Disgust at the same time, allowing the two forces to close on the chaos vessel, effectively shutting down its assault and locking it in place between the two vessels to be destroyed.

Meanwhile, Emperor’s Nightmare squads had flown into Hive Tertius and Hive Quartus. In a move that many will look back on as both one of the pinnacles of the chapter’s belief in shock and awe tactics, and a sign of impending sleeplessness, Sergeant Ariwan of the Night Owls called for a Thunderhawk drop directly into the primary shaft of Hive Quartus. An incredibly dangerous maneuver that cost the lives of almost a dozen marines. However, the move was extremely successful in completely disheartening the cultists mob, who have believed themselves safe from Nightmare intervention so deep underground.

The resulting battle went strongly in the Nightmare’s favor as the marines and Dreadnoughts of the Night Owls cleaved through the cultists, leaving not a single scrap of heretic in their path.

The assault on Hive Tertius had been different. Flawed One marines, including a chaos sorcerer had managed to reinforce the smallest of the hive cultists. The marines were using their chaos sorcery to devastate the population of Tertius, forcing young psykers into feedback loops that ended up destroying themselves and those around them. The majority of the marines who had survived the assault on Betten-Burgen had donned jump packs and moved both swiftly and silently to reclaim Tertius. In a rare occurance, two August Dreamwalkers in Iron had been awoken during the fight, and quickly prepped to be dropped directly into Tertius.

The combined psychic energy within Tertius was incredible, and unfortunately Tertius would see the greatest civilian loss of the hives the insurrection. Great waves of energy passed between the Dreamwalkers in Iron and the chaos sorcerer. With great strength of will, the two dreadnoughts willed the sorcerer off of this plane of existence, the sorcerer’s body ripped apart by the act of crossing between the materium and the immaterium so bluntly.

With the majority of The Flawed Ones’ marine forces in disarray, and their primary means of escape taken from them, the remaining cultists surrendered, most being burned or executed where they stood. In total, more than a full company’s worth of marines, sleepers and sleepless included, had been slain, including the loss of two dreadnoughts and a suit of the Nightmare’s treasured terminator armor.

The assault had been an eye opener for the Emperor’s Nightmares and close to a dozen marines who had been close to the imposters in the past took up penitence crusades into the Veiled Region to atone for being so blinded. Brother Damien would be granted highest honors post-mortem and have a grand statue built for him by his Sleepless Brethren that would stand as one of the great defenders of the chapter.