The cleansing operation in the underhive of the Hive World was proceeding in full swing, thanks to the combined efforts of the Astral Claws and the Helldivers.
Heretic cults lurking in the shadows, mutated creatures, and other elements of instability were being purged one by one under the Emperor's wrath. Yet, beyond the Hive itself, deep within the subterranean layers, another project of equal magnitude was being carried out with intense urgency.
Deep beneath the old industrial zone, the deafening roar of machinery and the mechanical shrieks never ceased. This was the secret base of the Helldivers and the Death Korps of Krieg—a strategic stronghold prepared for the upcoming Great Crusade.
When Marneus Calgar, Chapter Master of the Ultramarines, arrived in person to inspect the site following a detailed report—led by Ghostface—he found himself struck by the sheer impossibility of the scene, despite his mental preparation.
He had originally assumed that a subterranean project, however grand, would conform to the stereotypes of being dark, damp, and claustrophobic. Instead, what lay before him was a total engineering miracle.
A vast underground space had been carved out, with massive support pillars rising to hold the weight of the heavy rock layers above. The air was thick with the scent of earth, metal, and sweat, yet it lacked any suffocating sense of oppression.
High-powered arc lamps illuminated the area as bright as day, bringing every detail into sharp focus.
Calgar looked around. Beyond the shock, he felt a sincere respect for the near-obsessive efficiency and execution of the Helldivers and the Krieg. Working day and night, they had literally forged an unbelievable underground city in the depths of the earth.
The tunnels here were wide beyond imagination. The main artery Calgar walked upon was broad enough for two Leman Russ Battle Tanks to drive side-by-side, with ample room left for maintenance crews and infantry.
"Lord Calgar," Ghostface said, nodding slightly.
Calgar returned the nod, signaling that formalities were unnecessary. He reached out, lightly touching the cold metal of a nearby wall, feeling the immense strength contained within.
"This... exceeds my expectations," Calgar praised sincerely. "You have done well. However—"
He frowned slightly, asking with confusion: "I noticed these support structures. While massive, they don't seem to aim for absolute stability; some areas even appear a bit crude. Given the engineering prowess you've demonstrated, you could have built them to be far more indestructible."
The Helldiver's voice came through his mask: "Lord Calgar, we considered that. But no matter how many resources we invest or how many pillars we build, nothing can withstand the anti-matter bombardment of the Necrons. That power is enough to erase an entire Hive from the surface."
He paused before continuing, "Therefore, our requirement for the support structures is merely that they do not collapse immediately during the aftershocks of a Necron bombardment. This gives our armored forces enough time to deploy to the surface from these pre-set exits and launch a counterattack."
Calgar nodded thoughtfully, but soon raised a new concern: "If that's the case, isn't this too shallow? I fear it won't withstand a large-scale enemy bombardment."
Ghostface gave a light chuckle. "The Necrons will not conduct a large-scale bombardment here. Their primary objective is the extinction of sentient life, not mindless destruction. Even if all the Helldivers, the Krieg, and the Astartes gathered here, we would number only tens of millions. But the population of this Hive..."
Ghostface did not finish the sentence, but Calgar understood. The Hive's population, numbering in the tens of billions, was the Necrons' true 'target.' Compared to that massive baseline, they—the resistance—were but a negligible fraction.
The Necrons would not waste precious anti-matter bombs on a carpet-bombing of the entire Hive just to eliminate these 'tens of millions'; it would be too inefficient. They would choose other methods to erase life here.
Calgar looked at him. "No wonder you aren't afraid of potential retaliation from the nobility..."
He didn't wait for an answer, continuing to himself: "If the Hive of Amarah is to be completely destroyed by Necron bombardment, then the deaths of these nobles can be pinned entirely on the Necrons—serving as yet more evidence of their genocide against humanity. In this way, at least officially, you are disconnected from their deaths. The Helldivers remain perfectly hidden in this affair."
The Helldiver did not respond, standing quietly with an unreadable expression behind his mask. In truth, everything happening on Amarah was not just about resisting the Necrons for the Helldivers. They were also testing various systems, validating different social structures, and gaining practical experience to eventually transform their home world, Peditia.
Though Perditia had suffered greatly and its population had dwindled to dozens of billions, it remained a massive governance challenge requiring new models. While Calgar had promised to help them rebuild Perditia, the Helldivers knew they could not rely solely on the Ultramarines; they had to depend on themselves.
Seeing the silence, Calgar felt he had guessed the truth and did not press the subject. He turned his attention back to the engineering work.
"If everything goes according to plan and we have enough time to finish, there will be thirteen main arteries in total," Ghostface introduced. "It is expected to provide deployment space for 13,000 Basilisk self-propelled artillery pieces, 130,000 Space Marines, and 13 million mortal soldiers."
Calgar stopped in his tracks. It wasn't that he hadn't heard; he was confused by the recurring number.
"...May I ask why there are so many 'thirteens'?" he inquired.
Ghostface turned and answered earnestly: "We believe the number thirteen has a connection to the Emperor, Lord Calgar. The Necrons have reached the pinnacle of science; it is clearly unwise to go head-to-head with them on that front. Incorporating some metaphysical concepts might provide us with favorable conditions to defeat them."
"There's no need, truly no need," Calgar waved his hand, his tone nearly breaking. He had thought the Helldivers were flattering the Ultramarines, given the well-known connection between the number thirteen and the XIII Legion. "In the future, stick to rational engineering plans. Try to put less faith in metaphysics—we rely on steadfast will and masterful tactics, not ethereal superstitions."
Ghostface did not argue, thinking only to himself: In a few hundred years, even your father will start believing the Emperor is a God. That is just how this universe is.