For the next four months, the now-dubbed Reclaim Crusade successfully reconquered most of the fallen worlds.
Hundreds of traitor Astartes were slain.
Millions of cultists and traitor guardsmen died for their sins, paying in blood for choosing the path of darkness and daring to attack Camelarion.
World after world was reclaimed as Imperial forces pushed the enemy back.
Hive cities that had endured months of siege raised the Imperial Aquila once more.
Ports and manufactorums returned to loyalist control.
Supply routes were reopened, isolated garrisons were relieved, and countless stranded Cohort units were reunited with the main Imperial forces.
But now, Atharion had arrived at a different objective.
Instead of advancing directly toward Tri-Six, he found himself laying siege to a fortress world that had fallen to the traitors.
Voket.
A fortress world located in the northwestern regions of Camelarion, guarding one of the major warp routes leading toward Segmentum Pacificus.
Like all fortress worlds, Voket had been built to resist invasion.
In Camelarion's case, it had been designed not only to stop enemies from outside the realm, but also to contain any threat attempting to break out from within.
Its capital fortress was a massive defensive complex covered in weapon batteries, missile silos, anti-aircraft emplacements, and artillery platforms.
Yet one feature made it different from most fortress worlds.
Every major fortress in Camelarion possessed powerful void shield generators.
The system had originally been implemented as a precaution against Chaos Space Marines.
If traitor Astartes ever attacked, they would not simply be able to teleport directly into command centers and assassinate key leaders before the defenders could react.
The shields had served their purpose perfectly.
Unfortunately, they were now serving the traitors just as effectively.
The fortress remained protected beneath layers of overlapping void shields.
Orbital bombardment was impossible.
Teleport assaults were impossible.
Even Thunderhawk insertions had proven costly due to the sheer volume of anti-aircraft fire protecting the fortress.
As a result, Atharion had been denied the tactics that could have ended the battle quickly and was instead forced into a prolonged siege.
Fifteen Auxilia regiments had been committed to the campaign.
Ten infantry regiments.
Three armored regiments.
Two artillery regiments.
For the Astartes, other than the 1st Company and elements of the 9th Company, Atharion was joined by the 4th Company of the Raven Guard, the 5th Company of their successor Chapter, the Black Guard, the 6th Company of the Executioners, and the 3rd Company of the Flesh Tearers.
===
The ground shook continuously.
Whirlwind Scorpius batteries, Arquitor Bombards armed with Morbus Heavy Bombards and Spicula Rocket Systems from the 9th Company, Praetor Armoured Assault Launchers, Colossus Bombards, and Basilisks from the 10th Auxilia Field Artillery Regiment maintained an unending barrage upon the fortress.
Shells screamed through the sky.
Missiles left trails of fire.
Explosions covered the horizon.
Yet the void shield endured.
It had been two months since the siege began.
Two months of constant bombardment intended to overload the shield generators and create an opening for the Flesh Tearers and Executioners to storm the fortress with Auxilia support.
But the void shield showed no signs of failure.
Not a crack.
Not even a flicker.
The massive barrier continued to shimmer above the fortress as artillery shells and rockets detonated harmlessly against it.
"How long until your plan works?" the Flesh Tearers Captain growled as he stared at the fortress. "We have been sitting here doing nothing for two months."
"Well," Orion began calmly, "according to the original blueprints used for all Camelarion fortresses, the shield should have overloaded after two months of continuous bombardment."
"Should have?" the Executioners Captain asked.
"Should have," Orion repeated.
That immediately caught the attention of every Astartes present.
Atharion slowly turned toward the Librarian.
"You found something."
Orion nodded.
"I did."
With a gesture, he activated a nearby hololithic display.
The image of the fortress appeared.
Several sections began glowing red.
"The traitors are not relying solely on the fortress generators," Orion explained. "Not entirely. According to information gathered by the Raven Guard, my Librarians and I have come to the conclusion that the traitors sacrificed much of the world's civilian population and used the resulting warp energy to empower the void shield generators."
"So that is why the void shield never overloaded?" the Captain of the Black Guard asked.
Orion nodded.
"Three days ago, we felt a disturbance from within the fortress. It was as if the veil of reality had been sliced open."
His expression darkened.
"And immediately afterward, the void shield that we were certain would fail the next day regenerated completely. Since then, it has shown no signs of overload."
Silence filled the chamber.
No one needed Orion to explain what that meant.
The shield was no longer operating according to the laws of physics.
It was being sustained by Chaos.
Which meant the option of simply overwhelming it through bombardment was gone.
Atharion studied the fortress for several moments before speaking.
"Inform the Shadow Captain of the situation," he said, turning toward the Black Guard. "I want him to cause as much chaos as possible until we launch the main attack."
The Black Guard Captain nodded.
"It will be done."
"I will lead the 1st Company alongside the Flesh Tearers and Executioners in a frontal assault," Atharion continued.
The hololithic display shifted once more, revealing the entire battlefield.
The fortress dominated the center of the projection.
Red icons marked critical targets throughout the structure.
Weapon batteries.
Armories.
Food stores.
Command centers.
Void shield generators.
Surrounding the fortress were countless blue symbols representing the Imperial forces.
Entire regiments.
Artillery positions.
Armored spearheads.
The display was detailed enough to show individual companies and platoons.
Atharion pointed toward the western wall.
"The western wall is the weakest section of the fortress. It is likely where the traitors first captured it. The damage they caused has never been fully repaired."
Several sections of the wall lit up on the hololith.
"But how do we safely get past the lascannon batteries guarding it?" the Executioners Captain asked.
"I have prepared something for this situation," Atharion replied as he inserted a data-crystal into the holotable. "Though I did not expect to use it this early."
===
Shutting down the vox-channel, Shadow Captain Effe turned toward his Sergeants.
"Change of plan," Effe said in Corspake, "The void shield cannot be overloaded. We will do what we do best."
The Sergeants nodded.
"Understood."
"Copy."
"Confirmed."
One by one, they melted into the darkness.
To an outsider, it almost looked as if they had simply ceased to exist.
Within seconds, only Effe and his command squad remained.
The Shadow Captain looked toward the distant tower, the command tower of the fortress.
Since the arrival of the them, Atharion have send the Raven Guard to infiltrate the fortress, to collect information of the enemies and to sabotage the defense when the main attack begin.
The Shadow Captain have try to sabotage, or outright destroy the void shield generators when they first day after infiltrate the fortress.
But, all the generators, main and the secondaries are all protected by a large number of traitor guards and Death Guards. And with each of the generators also surrounded by Tarantula sentry guns that have been override by the traitor.
Even though they are able to destroy the garrison protecting the generators, the constant patrols around the generator chambers and other garrisons near them meaning that they will always have possibility to be trap within the chambers once the fighting begin.
And, worse for the Raven Guard, 4th company didn't arrive in full strength, as almost half of their company have been deploy to infiltrate the other worlds that have fallen to the traitors and rebels within Tempestus to support the effort of reconquering them.
"Let's go," Effe said towards his command squad, compose of one Sergeant leading nine Astartes, with a Apothecary alongside them. "it's time to purge the traitors."
===
For the next five days, the battle continued as usual.
The artillery and rocket barrages continued relentlessly, allowing the traitors to believe the loyalists still had not discovered the true reason behind the void shield's resilience.
Inside the fortress, however, the deaths of patrols and officers had begun to attract attention.
Yet little was done to address the problem.
The fortress housed not only Death Guard traitors, but also numerous followers of Khorne. Violence between the different factions was common even when there's common enemy just on the other side of the wall.
Many of the bodies were found torn apart by chain weapons or beaten to death with bare hands.
As a result, most of the traitors simply assumed their allies were killing one another.
Exactly as the Raven Guard intended.
Of course, the reason Atharion delayed the final assault was not solely to allow the Raven Guard to cripple the traitor command structure.
He also needed time to prepare.
===
"How are the machines?" Atharion asked.
The Warsmith stood beside a massive armored vehicle, typing commands into a datapad while two servo-arms and four mechadendrites worked around the machine.
"We have calmed their machine spirits and completed all required maintenance," the Warsmith replied as he looked up from the datapad.
"Good."
Atharion nodded and looked up at the towering vehicle before him.
"Then we launch the attack today."
In front of them is the Mastodon, the heavy tank that use by the Legioness Astarte during the Great Crusade and the Horus Heresy. it's a tank far larger than the Land Raider. One of the largest transports of the Legiones Astartes, it was even equipped with void shields to protect it and its occupants from harm. These power-fields were powerful enough to block Autocannon shells and even Lascannon blasts.
For the weapon, it's commonly equipped with a forward Siege Melta Array, a turret-mounted Skyreaper Battery, two sponson-mounted Heavy Flamers, and two sponson-mounted Lascannons. It also can be equipped with up to four Hunter-Killer Missiles.
It's an ancient war-machine that have disappear from the battlefield since the end of the Heresy, even saw little to no action during the Scouring among the Loyalist rank. While, the situation of the war-machine in the Traitor rank are unknown, Atharion does think that they still have a number of Mastodons laying around, just that none of them willing to use it.
"You intend to deploy all of them, my lord?" the Warsmith said slowly.
"Yes," Atharion nodded. "I want whole 1st company to be deploy, not to said there's also the Flesh Tearers, Executioners and even the Black Guard I need to make sure can arrive safely to the position."
Indeed, while previous plan is that the Black Guard will wait behind and then advance along side the Auxilia once the breach is confirm. The Black Guard Captain later come to meet with Atharion personally after the meeting, argue that they need to strike the fortress wall with everything they have as the time is running low, so that there's no reason for them to stay behind and not attacking with them.
Not wanting to disregard a potential allies and one of the few successor Chapter from the Raven Guard, and they indeed running low on time.
Every day spent at Voket was another day Pestigor continued his work within the Tri-Six System.
If the final assault was coming, then every available Astartes should be committed to it.
And more importantly, they have volunteered. It's might be insulting or dishonored for one to refuse such request, even when it come from a Chapter come from a gene-line that also famous for their rational thinking.
"Won't it be risky if we show them these?" the Warsmith asked, gesturing toward the Mastodons.
Not merely the one standing before them.
But all twenty-two Mastodons housed within the massive temporary hangars that had been constructed to conceal the ancient war machines.
"It will make them suspicious of our Chapter."
"It might," Atharion admitted with a nod.
His eyes swept across the row of colossal vehicles.
"But their honor will prevent them from spreading word of it."
The engines of several Mastodons growled as Techmarines completed the final rites of activation.
"They will report what they have seen to their Chapter Masters," Atharion continued. "That is expected. But as long as we remain loyal to the Emperor and do not threaten the Imperium, they will keep such knowledge confidential."
The Warsmith remained silent.
Atharion glanced toward him.
"Especially when we have supplied them."
A faint smile appeared on his face.
"New power armor. Weapons. Ammunition. Spare vehicle parts."
The Warsmith let out a metallic chuckle.
"Bribery?"
"Support between allies," Atharion corrected.
"Of course, my lord."