Fabius Bile felt a pang of shame.
Back when the Blight plagued the Legion and his primarch entrusted him with the heavy burden of curing those hundred-odd battle-brothers, he had failed to deliver.
Later, those brothers made a complete recovery through the Warmaster's Primaris transformation surgeries, allowing Bile to break free from the torment of the Blight as well.
During those dark years, he had conducted countless underhanded experiments behind Fulgrim's back, grossly violating the honor of the Emperor's Children. The gravity of Bile's unsanctioned trials extended far beyond Legion politics; had the wider Imperium investigated his secret work, his head would have been forfeit.
Yet Fulgrim and his battle-brothers had covered for him time and again. Exposing such unsavory practices would have brought deep dishonor upon the entire Legion, and ultimately, he had pursued those dark paths solely to save his brothers.
It was this unspoken brotherhood that allowed Bile to survive to this day.
Ever since Perturabo assumed the mantle of Warmaster, institutional oversight had relaxed slightly.
Rather than outright leniency, it was a tacit understanding within the framework of rules to turn a blind eye to minor infractions that blurred the line.
Strictly speaking, this served as a modest perk to compensate the Space Marines for remaining isolated from the Imperial bureaucratic machinery, and Bile was one of its primary beneficiaries.
Although his secret experiments remained strictly classified, the others tacitly agreed to refrain from condemning his research.
Unsanctioned genetic experimentation was exceptionally widespread across the Imperium. Cruel as it was, his work undeniably served the Imperium's greater good. Still, since such matters could never be brought to light, Bile had always treaded with utmost caution.
For years, he had walked on eggshells, never daring to cross the line. He simply couldn't afford to bring shame upon his Legion should a scandal ever erupt—a disgrace Fabius Bile refused to cause.
What truly planted the seed of temptation in Bile's mind regarding his experiments occurred during the Retribution Crusade.
During that campaign, he encountered those Chaos-corrupted Astartes. The traitors themselves and their gene-seed were in a wretched state.
Prone to high mutation rates and appalling instability, their gene-seed had suffered irreversible corruptions that rendered it entirely unusable.
It was only after performing autopsies that Bile realized many of these traitors did not originate from a single Legion; they were merely a patchwork hodgepodge thrown together.
Members from every conceivable Legion were present, their gene-seed largely pillaged from other warbands.
The only ones in relatively decent shape were those Ultramarines. Even though Roboute over on the other side had ascended as the Dark King, his forces hadn't abandoned their physical flesh like those other fools. As a result, his Ultramarines suffered no shortage of gene-seed.
Their lineage remained stable and unbroken, much like Bile's own Legion.
This chaotic state of affairs persisted to this day. Many traitor warbands were "patched-together groups" in every sense of the term; very few could field a cohesive force of true native Legion remnants.
This realization led Bile to a bizarre, strangely eccentric train of thought.
Under normal circumstances, when Space Marines from the major Chapters witnessed these makeshift traitor warbands, they would react with nothing but contempt and mockery—deriding the traitors as mere scum who couldn't even rally enough proper battle-brothers to mount a decent rebellion against the Imperium.
But Bile saw things differently. He pondered: the production requirements for an Astartes were extraordinarily stringent, to the point where replacing losses had become exceedingly difficult.
Why not directly create female Astartes, allow them to pair together, and grant Space Marines the ability to reproduce and propagate naturally?
After all, Space Marines were merely disinterested in carnality on a psychological level; it didn't mean they had actually lost their physical capacity for it.
Bile believed his battle-brothers would understand, provided it was presented as a necessary sacrifice for the Imperium and the Chapter—a vital measure to reinforce the Space Marines' severely depleted numbers.
And so, he put his theory into practice, harvesting numerous young girls of suitable age to serve as test subjects.
This marked the true breach of taboo—a monumental event the Imperium could never tolerate.
Bile proceeded with extreme caution, terrified that his secret experiments might be exposed. To safeguard his work, he didn't even dare use Abominable Intelligences for assistance, nor did he record any experimental data in electronic formats to prevent leaks.
The surgical procedures to transform these subjects were fraught with failure. The young girls suffered overwhelming organ rejection, and with no historical precedent for female Astartes, Bile was effectively forging a new path blindfolded.
It was a stroke of fortune that Perturabo had standardized the emergency resuscitation protocols for these transformation procedures. Otherwise, merely disposing of the bodies without alerting his battle-brothers or the local AIs would have proved an insurmountable task for Bile.
As for the sudden appearance of several female serfs within the Legion, his battle-brothers thought little of it. They were viewed merely as failed surgical candidates or ordinary mortals—hardly worth a second glance.
Bile's secret experiments continued in the shadows until the day the Legions were officially split into Chapters: Bile finally succeeded.
A young girl successfully weathered the rejection reactions of all nineteen surgical implantations. Though Bile had made minor adjustments to the girl's physiological structure for these operations, she remained the sole subject to survive the process intact.
Bile was ecstatically overjoyed with his creation. For any scientist, pioneering a groundbreaking invention that had never existed before was a source of supreme pride.
Yet what followed the initial high was a cold, creeping dread. Before a theory became reality, human ambition and audacity knew no bounds, driving one to sacrifice everything to achieve a crazy goal.
Once that goal was realized, however, the impending consequences proved to be a crushing headache.
Having achieved his goal and secured a viable prototype, Bile naturally wanted to protect this hard-won success.
He knew all too well how shocking and world-shattering this revelation would be if exposed to the galaxy.
It wasn't merely that female Space Marines could exist; rather, no one could bear the catastrophic chain reaction that a female Space Marine's existence would unleash.
It implied that Space Marines could break away and form an entirely independent sub-species of humanity, much like the abhumans.
Only far stronger, more intelligent, and vastly superior.
Bile had verified the data: female Space Marines were capable of normal conception!
This meant Bile had opened a brand-new path for the Astartes—one that could stir countless dangerous ambitions in their minds.
The blow to the Imperium would be absolute and lethal. Unquestionably, should this secret be exposed, it would rank as a monumental crisis on par with the ancient Cybernetic Revolt or the Chaos Heresy.
Because Space Marines would finally be able to reproduce independently.
No one knew whether the offspring born from such a union would be classified as baseline humans or Astartes.
Human-Eldar hybrids had existed in the past; certain individuals who fought shoulder-to-shoulder with the Aeldari had naturally developed feelings for one another over time.
While the Aeldari were technically classified as abhumans by some, severe reproductive isolation still existed between the two species. To preserve the fruits of their love—and as part of the Aeldari's experimental efforts to integrate into human society—they combined their genetic material in laboratories.
Utilizing a mix of Aeldari technology and leftover Dark Age tech from humanity's Golden Age, a few half-Eldar, half-human hybrids were brought into the world.
These children exhibited clear psychic signatures at birth, possessed physical durability far exceeding that of ordinary human infants, and leaned closer to humans in both appearance and temperament. Most importantly, these hybrid children were capable of becoming Space Marines!
In other words, their genetic foundation remained predominantly human, merely laced with beneficial Aeldari genetic fragments that yielded positive adaptations.
They could be considered relatively successful hybrids. Though they inevitably faced minor discrimination due to their origins, it remained largely manageable.
Space Marines, however, were a completely different story—they possessed the potential to irrevocably alter the course of human history.
Humanity relied on the Space Marines, and the Space Marines relied on humanity. While all belonged to the human species in principle, the arrogance of the Astartes was undeniably real.
The emergence of a female Space Marine threatened to corrupt this delicate balance entirely.
If Space Marines began bearing their own children, passing their lineage down through generations while their numbers swelled, how would ordinary mortals view them? And how would these second and third-generation Astartes view the rest of humanity?
Would they view themselves as superior beings? Or would they commit atrocities against baseline humans that would give even the human-supremacist Emperor a brain hemorrhage?
If handled poorly, a devastating civil war among humanity would become absolutely unavoidable. No single individual could shoulder such terrifying responsibility—not even the Emperor or Perturabo.
As the perpetrator, Bile's fate would be far worse; being executed by a thousand cuts would be considered a merciful punishment.
Initially, anxiety gripped him, prompting thoughts of destroying the experimental subject to erase the evidence. After all, he had proven his theory—female Space Marines were indeed possible. Now that the procedure had succeeded once, replicating it in the future would be simple enough.
All he needed to do was back up the experimental data, monitor the Imperium's political climate, and decide later whether to resume the project.
That was Bile's plan, yet as he looked upon the prototype he had created with his own hands, he found himself unable to bring himself to destroy her.
When the female Space Marine unexpectedly called him "Father" for the first time, Bile's resolve dissolved entirely.
And so, he kept the child by his side. After backing up the experimental data, he thoroughly scrubbed every trace of his previous trials from existence.
He named the child Melusine, adjusted her Primaris transformation procedures, and assigned her a role within his staff. Otherwise, her physical size alone would have raised immediate suspicion.
From that day forward, an apothecary apprentice appeared at Bile's side. Many grew curious about this taciturn "brother," wondering who could possibly earn Bile's exclusive favor.
Yet Bile deflected their subtle inquiries, and the others eventually let the matter drop.
For a time, all seemed peaceful. Melusine understood the sensitivity of her true identity and dutifully followed Bile as an obedient apprentice.
She grew at an astounding pace, and even Bile felt a surge of pleasant surprise at his daughter's innate talent in the medical arts.
She possessed the potential to become an apothecary rivaling himself in skill, but that proved to be a double-edged sword. After all, fame attracted unwanted scrutiny; if Melusine exposed her true identity because of her brilliance, it would spell disaster.
Thus, Bile strictly forbade Melusine from displaying her true capabilities in public, preventing her from drawing unnecessary attention even when she was fully capable of performing complex tasks.
Bile protected Melusine with utmost care, keeping her identity hidden even within their parent Legion, the Emperor's Children. Over the years, Melusine caught glimpses of her genetic father on multiple occasions.
She finally understood why her master held such awe and fanaticism whenever he faced their Primarch. No one could stand before a Primarch without being captivated by their overwhelming aura—and Melusine was no exception, especially with that Primarch being Fulgrim himself.
Fulgrim paid little mind to this obscure apothecary apprentice. With Bile deliberately steering his attention elsewhere, the Primarch never questioned the identity of this child who never removed her helmet.
Bile and Melusine walked on eggshells, fully aware that exposure meant complete ruin.
Yet despite all his meticulous calculations, Bile never foresaw that certain individuals cared nothing for Chapter protocols—individuals who actively thrived on stealth and mischief.
Trazyn possessed countless surrogate bodies scattered across the galaxy. An Adeptus Mechanicus Tech-Priest embedded aboard the flagship of the Emperor's Children went completely unnoticed, even forging several friendships among the Astartes by crafting novel gadgets in private.
This was a pastime Trazyn had always enjoyed: a tiny gesture of goodwill yielded abundant friendships, making him feel truly alive.
For years, Trazyn had paid little mind to Bile's unsanctioned activities. That was until one day, while passing by Melusine, a sudden spike of anomalous data metrics caught his attention.
Deploying a fraction of his Necron technology, Trazyn saw right through the disguise, uncovering the true identity of the little apprentice following Bile around.
The discovery energized Trazyn instantly. A female Space Marine! Truth be told, nothing in the galaxy possessed greater collection value than this.
Female Custodes numbered in the dozens, yet there wasn't a single female Space Marine in existence. The Astartes standing behind Bile was, without a shadow of a doubt, a one-of-a-kind original.
If he could add her to his collection, his museum would gain yet another artifact of monumental historical significance.
And so, Trazyn hatched a mischievous scheme.
However, Fabius Bile was no pushover. Just as Trazyn attempted to catch the apprentice off guard—planning to knock Melusine unconscious and stuff her into his museum while Bile was away reporting to Fulgrim—the warning system Bile had secretly installed was triggered.
Trazyn's makeshift body was caught red-handed on the spot, and in the ensuing commotion, Melusine's true identity was accidentally exposed to the Legion.
A massive shockwave rippled through the Emperor's Children. While Fulgrim and Vespasian managed to temporarily suppress the news—wrestling with how to resolve the crisis and report it to the broader Imperium—Trazyn acted immediately.
Having failed his initial capture attempt, Trazyn decisively leaked the entire affair directly to the Emperor and the high council. In an instant, the crushing headache shifted straight to Perturabo and his inner circle.
As for the revelation of a female Space Marine, Perturabo could only sigh: that bunch of scientists was simply far too insane.
Even though his own genetic modifications back in the day were wild, he had never dared to cross major ethical boundaries. Unlike those reckless fools, who acted with zero restraint.
Now, the situation had escalated into a massive crisis, leaving them with an immense headache to resolve.