Months melted away within the confines of the hidden laboratory.
After he had safely returned Minazuki, he had other pressing matters to attend to. The schematics from Szayelaporro's data had proved invaluable, offering an insight into the twisted genius beneath the Arrancar's madness.
However, Silas knew mere imitation wouldn't suffice. He sought not to copy Szayelaporro's creations but to surpass them, to bend them to his own meticulous design.
The workbench had morphed into a sprawling landscape of intricate diagrams, gleaming vials filled with strange concoctions, and scattered apparatus buzzing with spirit particles. He worked feverishly, the Hōgyoku's power fueling him as he delved deeper into the secrets of Szayelaporro's research.
This was unlike the times he’d looked over Kisuke’s research. Szayelaporro’s knowledge came from his extensive days as a Hollow. But that didn’t mean Silas wouldn’t adapt.
The first step involved replicating Szayelaporro's serum, a compound designed to shield Hollows from the devastating effects of poison—the thing in which Szayelaporro specialized.
It was a meticulous process, requiring a delicate understanding of both Hollow physiology and the corrosive nature of various poisons. Silas worked tirelessly, the Hōgyoku's influence subtly guiding his hand, allowing him to recreate the serum in a matter of weeks rather than the years it would have taken an ordinary scientist.
Yet replication was mere child's play.
Silas saw room for improvement, including ways to make the serum more potent, faster-acting, and resistant to a wider variety of toxins. With each iteration and each tweak of the complex formula, the serum grew stronger, a marvel of biological and spiritual manipulation.
But mere poison resistance wasn't enough. To truly counter the diverse capabilities of a Soul Reaper, versatility was key.
Silas turned his focus towards another of Szayelaporro's creations—a vaccine designed to protect the outer layer of a Hollow’s skin against the ravages of the elements, from the scorching heat of a desert to the frostbite-inducing cold of Hueco Mundo's perpetual night.
He studied the formula, his eyes scanning the molecular structures and the delicate interplay of spirit particles and raw materials. With a deft touch and the Hōgyoku's latent power, he began to alter the design, transforming it into something far more durable.
The first batch failed, much to Silas’s disappointment. Only after recalling Szayelaporro's abilities did he understand why he was unsuccessful.
Szayelaporro was an Arrancar who squarely used poison, illusions, and traps. He was akin to that of a parasite, having the ability to possess someone’s nervous system and then consume it from the inside until he’s reborn.
It was easy to make the poison resistance batch with his mindset, but this elemental resistance had to work differently.
He reintroduced elements from his own research, a unique blend of regenerative compounds designed to withstand extreme conditions. After a couple more months, he had succeeded.
This new serum wasn't a mere shield; it would turn the very surface of Hollow’s flesh into a dynamic, adaptive armor—much stronger than an Arrancar’s “Iron Skin” ability.
This ability is a defensive technique in which the user condenses their spiritual powers to create extremely tough skin. This hardened skin is strong enough to block attacks from Zanpakutō, allowing users to fight them directly.
Additionally, Iron Skin is not impenetrable, and skilled opponents can adapt their attacks to overcome it, as demonstrated in a battle that took place between Zaraki and Nnoitra.
The strength of an individual's Iron Skin is generally linked to their spiritual pressure. But with this vaccine, they could enhance their Iron Skin with an added layer of protection. Its efficacy was such that it would require the flames of Yamamoto’s Ryūjin Jakka to inflict any significant damage.
Two months were spent painstakingly perfecting this new protective vaccine, and still, Silas’s drive was unyielding. His thoughts lingered on Nel’s childish form.
So he began to dissect the notes Szayelaporro had scribbled regarding all of the Arrancar’s in Las Noches. There was hardly any information on anyone.
All it detailed were their abilities, something Silas had extensive knowledge of. To be fair, the notes weren’t even worth his efforts. Unlike Szayelaporro, who only knew of his comrades’ outer abilities, Silas knew of their innate and hidden ones.
Chillingly, he destroyed the notes, finding them unworthy of his time.
That did not mean he would give up, though. Nel possesses some intriguing powers that make her stand out from other characters.
For instance, her saliva has mild healing properties. Even more impressive is her ability called “Cero Doble”, which allows her to swallow an enemy's Cero attack and then fire it back with even greater force.
Even in her weakened child form, she can still absorb and redirect these energy blasts. There's a peculiar detail about this: whenever Nel uses her Arrancar abilities, her mask glows, even as a child.
For Silas to restore her to her adult form, this piece of information is crucial. This is because her form has reverted within her broken mask. Finally, there was the special armband created by Kisuke Urahara. By helping her contain her spiritual powers, the device allowed her to maintain her adult form.
Identifying the compounds used to suppress Nel’s growth and stunt her powers could be recreated.
There were two options: dismantle the effects, a slow and uncertain process, or counteract them, a far riskier but potentially complete reversal. Risk was something Silas thrived on.
Utilizing his understanding of Hollow physiology and spiritual manipulation, he reverse-engineered a new serum, a formula bursting with reformative latency and raw power tailored to counter the debilitating effects inflicted on Nel.
It was not going to be a device, which was stated to be temporary, but a full restoration of her adult form.
This took another grueling month of trial and error to push the Hōgyoku's transformative power to its very limits. When the final vial shimmered on the workbench, its contents an iridescent green, it was clear that Silas had perfected both science and will.
He knew that these serums, potent as they were, were merely one step towards his grand goal. But each discovery, each breakthrough, reinforced his confidence in his newfound abilities. Every successful experiment was a testament to his growing use of the Hōgyoku, a power he would eventually turn into the ultimate weapon.