Chapter 424– Sudden Upheaval! An Inevitable Civil War Within the Imperium!
Amon immediately activated the Thousand Sons' broadcast channel and displayed the contents of the letter. With a rousing voice, he issued a stirring proclamation to the warriors of the Legion:
"Warriors of the Thousand Sons! Today, we suffer unjust humiliation on Prospero. They seek to deceive and betray us with treacherous schemes!"
As Amon's impassioned words rang out, the confused warriors of the Thousand Sons seemed to find their anchor once more. One by one, their eyes regained focus and resolve, listening intently to his speech.
"Now, they aim to burn everything here, to erase every trace of our Legion's existence! There is no longer any path of retreat!"
The Astartes warriors stared at the content of the letter, overwhelmed with disbelief. A swirl of complex and conflicting thoughts surged in their minds.
The pain of personal injustice clashed with their loyalty to the Imperium, creating two irreconcilable beliefs that warred violently in their hearts.
The Emperor had issued an Exterminatus on their homeworld, Prospero. Were they still expected to serve him as loyally as before?
At that moment, Amon's voice rang out at precisely the right time: "Only by fighting to the death… can we defend our homeland."
The warriors of the Thousand Sons froze for a moment. They looked down in silence, not immediately responding. But their clenched fists told a different story—they had already made their choice in their hearts.
…
Meanwhile, aboard the flagship of the Death Guard Legion, Mortarion had just received news from the surface of Prospero.
The enraged warriors of the Thousand Sons had killed the investigators sent to examine the flesh-mutation incident. This self-incriminating action left no doubt—they had committed treason and rebellion.
"So… they're dead set on betraying the Imperium."
Mortarion could not hide his elation. Hands clasped behind his back, he stood before the viewport, watching the Thousand Sons' fleet maneuver into position, thinking to himself that he could now destroy these Imperial heretics without guilt.
Had the Thousand Sons cooperated with the investigation, and with Guilliman's moderating presence, Mortarion might never have found an excuse to act.
But now that they had rebelled, it was the perfect time to strike and wipe them out.
In low orbit above Prospero, the Thousand Sons' ships moved swiftly and in tight formation.
They had adopted a classic Imperial defensive posture, clearly preparing to withstand an assault from the forces of four Primarchs.
Mortarion wasn't surprised by their decision.
If he had been in their position, he might have rebelled too.
Of course, if he were the one rebelling, he would've done it under the banner of "cleansing the court of corrupt advisors," a noble-sounding pretense to mask a direct strike against the Emperor.
It was simply more convenient for political maneuvering later.
"The Thousand Sons, gone just like that. What a waste," muttered Durak Rask with a curl of his lip. There was a hint of sympathy for the fallen Legion's fate—but also a trace of mockery for their futile resistance.
As the Death Guard's Master of Ordinance, Durak was well aware of the Thousand Sons' past contributions. They had eliminated many stubborn psyker-mutants in the name of the Imperium.
Even the Chaos Gods and their daemons in the warp were wary of the Thousand Sons' power.
Unfortunately, this once-glorious Legion was about to be consigned to the dustbin of Imperial history.
"That old man's as heartless as ever… but he made the right call this time," Mortarion added calmly.
In truth, his relationship with the Emperor had never been good.
When the Emperor first found him, he'd demanded Mortarion assault the fortress of the xenos overlord known as the Pale King alone. Yet just as Mortarion was locked in a life-or-death battle with the creature—
—the Emperor intervened and killed the Pale King himself, all in the name of protecting Mortarion.
This infuriated him beyond measure.
The Pale King had been Mortarion's adoptive father, though he had never treated Mortarion as a son. Infinity poison experiments and brutal military training had left Mortarion to survive in constant agony. All he knew was killing—he had never experienced familial love.
His sole wish was to one day slay his foster father with his own hands, to claim everything the Pale King possessed:
The glory of a warrior, the territories of Barbarus, and the loyalty of his soldiers.
But the Emperor's well-meaning "kill-steal" shattered Mortarion's chance to fulfill that ambition. It nearly broke his very will.
After killing the Pale King, the Emperor simply took everything Mortarion had worked for—Barbarus, the prestige of slaying the xeno lord, and the allegiance of his army.
Mortarion had wanted to forge his legacy with blood and steel, to build a political foundation with the Pale King's head as the cornerstone. But the Emperor had demolished all of it.
That incident became Mortarion's eternal emotional scar. Even though the Emperor granted him the honor of being a Primarch, Mortarion never truly accepted him, nor regarded him as a father.
Now, through the Exterminatus Order on Prospero, Mortarion was more convinced than ever that to the Emperor, they were nothing but tools.
Family? What a joke.
"Magnus, that poor bastard," Mortarion sneered with a bitter grin. "After going missing, that old man didn't even send anyone to search for him. Instead, he sends me to annihilate Prospero."
Among the Primarchs, Magnus had been one of the few truly favored by the Emperor—even embraced by him.
Even Horus had been jealous of that affection.
But the higher you fly, the harder you fall.
The Emperor's own hand signing the Exterminatus, juxtaposed against his former love for Magnus, painted a brutally ironic picture.
"Open fire. Sink those troublesome ships," Mortarion commanded.
"My lord, we haven't even informed the other Primarchs. Acting unilaterally like this—aren't we overstepping?" said Typhon, Mortarion's second-in-command, trying to dissuade him.
As the commander of the Death Guard's First Plague Company, Typhon's resistance to toxins and battlefield prowess were nearly on par with Mortarion himself.
It was precisely for these reasons that Mortarion had chosen him as a trusted lieutenant.
Within the Death Guard, Typhon's status was second only to the Primarch himself.
"Open fire."
Mortarion did not respond with anger to his subordinate's objection. Without even turning his head, he repeated the order in a low, cold voice that radiated oppressive finality.
His rasping tone and detached manner made it clear to Typhon—there was no changing his mind.
"Yes, my lord…"
Typhon was helpless. This report would be hell to write. With their Primarch acting on his own, the rest of them were bound to suffer the consequences.
Soon, under Mortarion's orders, the Death Guard's shipboard cannons began charging rapidly.
From the front ranks of more than 300 warships, arrays of main cannons began to glow brightly. Swarms of conventional missiles and explosive payloads launched with blinding flashes, streaking toward the Thousand Sons' fleet.
This sudden development naturally caught the attention of the other Primarchs.
[Mortarion! What are you doing?! You opened fire without permission!]
Guilliman's voice came through the comms, filled with reproach.
As the overall commander of this operation, he had the authority to direct the actions of the other Primarchs.
Mortarion's actions were undoubtedly an overreach of authority.
"I sent investigators down to the surface, and they were slaughtered by the traitors below. The Thousand Sons received our orders and not only refused to disarm, but have mobilized their forces in open defiance."
"This is a blatant insult and disregard for the Emperor's command. I have the right to teach these mutts a lesson—to send them a warning."
Mortarion had already branded the Thousand Sons as traitors. And with the investigators confirmed dead, even Guilliman had no grounds to argue.
After all, the team he dispatched had also vanished without a trace. They had likely been killed.
"Mortarion—!"
"I must remind you once more that I am the designated commander of this joint operation—by direct order of the Emperor himself."
"You were to consult with me before taking any action, not act on your own initiative like this!"
"I am ordering you to cease fire immediately and withdraw from the war zone!"
Guilliman's voice was righteous and firm. From the beginning, the plan had been to handle things objectively—wait for full intelligence from the investigators, send additional envoys to de-escalate and establish dialogue.
There might still have been a path toward peaceful resolution.
But like many other Primarch Legions, the Thousand Sons were known for their decisiveness and ruthlessness. Once blood was shed, it would be a fight to the death.
The worst kind of war was one where both sides were unwilling to back down.
And now, with Mortarion's preemptive strike, he had made their position unmistakable—the Exterminatus was real.
There would be no turning back now.
"They've clearly defied the Emperor's command. If the Thousand Sons want death, we'll grant them their wish."
Leman Russ sided with Mortarion. To him, the act of resistance was already full-blown betrayal. And traitors to the Imperium?
They all met the same fate: execution.
"Guilliman, I formally request authorization for the Space Wolves to engage. We will crush the Thousand Sons' void forces." Leman Russ spoke out coldly.
Lion El'Jonson remained silent. His only assignment was to ensure that Mortarion didn't kill Magnus by mistake. The lives of the Thousand Sons warriors? That wasn't his concern.
If Mortarion wanted to vent his anger, so be it.
But seeing Russ stepping into the fray as well, Guilliman quickly turned his gaze toward the Thousand Sons' position.
As expected, in response to the Death Guard's initial assault, the Thousand Sons' ships were now powering up their weapons.
And their targeting systems had locked onto ships from all four Legions—Dark Angels, Death Guard, Space Wolves, and the Ultramarines.
Guilliman felt a wave of despair wash over him.
So, it had come to this after all.
The worst-case scenario had happened.
"…Fire."
He sighed in resignation.
The next second, the elegant, hammer-shaped warship Glory of Macragge swiveled and aimed its massive cannons at the Thousand Sons' flagship, photep.
Unlike other Primarchs who lacked interest in administration and infrastructure, Guilliman had poured considerable resources into the construction of his flagship.
As a result, its destructive power far exceeded anything the Death Guard could field.
…
Meanwhile, Amon had fully assumed command of the Thousand Sons Legion. All those still loyal to the Emperor had already been detained and locked away in the dungeons of Prospero.
Though Amon held complete control of the Legion, his mind was far from at ease.
The latest reports indicated that the Megacorp had sealed off the entire Prospero system with an iron grip.
Though the Megacorp's commanders had stated they wouldn't stop the Thousand Sons from retreating, they had completely locked down the Mandeville Point—the critical exit into the warp.
Without access to the warp lanes, the Legion's ships wouldn't get far on conventional drives alone.
And to make matters worse, they were facing four Primarch-led Legions—not exactly a fair fight.
The Thousand Sons had many powerful psykers, but against four Primarchs at once?
It wasn't hard to guess how that would end.
If Magnus were still around, they might have stood a chance of holding the line by relying on his formidable warp mastery.
But here on this isolated battlefield, they had only themselves—the desperate remnants of the Thousand Sons.
"No! I won't fall here!"
Though Amon was under immense psychological pressure, he forced himself to endure.
He was now the last hope of the entire Legion. If he faltered, they were finished.
"They've realized we won't surrender."
After a moment of thought, Amon issued his next command: "Change formation! Protect the Photep"
The flagship was the heart of their fleet. If it fell, the entire Legion would collapse.
"Yes, sir!"
The warriors of the Thousand Sons answered in unison.
Amon turned back to the screen, continuing to monitor the tactical display. In his mind, the ending to this battle had already become clear—there was only one outcome.
The Thousand Sons would be destroyed.
But better to die standing than live kneeling!
"Emperor… why have you done this to us?"
Amon's heart ached. Even now, he could not accept the Emperor's judgment.
The Thousand Sons—and Prospero itself—had long been the Imperium's greatest reservoir of psychic knowledge and arcane technology.
Some interaction with the warp was inevitable in such a place.
And even if some contamination existed—so long as it was controlled, wasn't it manageable?
All Amon wanted now was to lead his Legion to Holy Terra itself, to stand before the Emperor and prove to him that they were not tainted by Chaos.
But such a dream was far from reality now.
"Report! The Death Guard have started their attack!" came a shout from one of the crew.
Not that it was necessary—Amon had already seen the flood of incoming lights through the viewport.
It had begun.
The civil war within the Imperium was now unavoidable.
"Hold formation! Return fire!"
Amon gave the order without hesitation.
This was Prospero—their home. The Thousand Sons still had ample supplies and resources here.
As long as they could hold out, there was still hope.
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