Hueco Mundo, a desolate land shrouded in eternal night, was covered in an endless expanse of white sand.
At the center of this lifeless wasteland, a magnificent, pure white palace rose from the ground.
It was a fortress constructed of Reishi, the center of power symbolizing the new order of Hueco Mundo.
Las Noches.
In the deepest reaches of Las Noches, upon a lofty throne that overlooked the entire grand hall...
Sosuke Aizen sat with his legs casually crossed, resting his chin on one hand as he quietly gazed upon his new territory.
His deep brown eyes no longer held their former gentleness; instead, they were filled with an arrogance that looked down upon all living things, treating everything in the world as mere chess pieces.
"It truly is a splendid view, isn't it? Gin, Kaname."
Aizen turned his head slightly, his calm voice echoing through the cavernous hall.
Below his throne, Gin Ichimaru sat on the floor out of sheer boredom, his hands tucked into his wide sleeves.
On the other side, Kaname Tosen, wearing his visor, stood as straight and silent as a statue.
"My, my, you are absolutely right, Lord Aizen," Gin said with a smiling face, his tone carrying a hint of playful mockery. "However, compared to this empty palace, I still think the previous spectacle of the changing of the guard was far more entertaining."
A faint smile touched the corners of Aizen's lips.
Years ago, when he brought the two of them to this land to prepare for their future defection, it had drawn the ire of Baraggan, the self-proclaimed King of Hueco Mundo.
Baraggan had expressed extreme fury and contempt toward these three uninvited Soul Reapers.
Thus, the skeletal emperor sitting upon his throne of bones had foolishly challenged Aizen.
The result, naturally, was overwhelmingly one-sided.
Before Aizen's absolute hypnosis, which could deceive anything and everything, the so-called King of Hueco Mundo was nothing more than a pathetic, laughable fool oblivious to the wider world, drowning in his past glory.
"Baraggan is indeed an interesting specimen. His ability to manipulate senescence touches upon the laws of time to some extent," Aizen remarked, as if critiquing a slightly flawed piece of art. "It is just a pity that his vision was far too narrow."
"How could a wraith, content with building a throne upon bones, ever understand the true meaning of evolution and godhood?"
Aizen slowly stood up and descended the steps of the throne.
"Still, subjugating his power to serve as the foundation of our new order is barely acceptable."
"Otherwise, we wouldn't have had so many Menos Grandes assisting us in our escape from the Seireitei."
At this, Aizen touched the already healed wound near his eyebrow and smiled.
Kaname Tosen bowed his head slightly, his tone filled with fanatical devotion. "Everything is for the great cause you have envisioned, free from hypocrisy and oppression, Lord Aizen."
Aizen smiled as he walked past Tosen, patting him on the shoulder. "Let us go."
"Today, a grand event bordering on a miracle awaits us."
The three of them traversed the intricate, seemingly endless white corridors of Las Noches, making their way toward the quiet underground laboratory.
Aizen was indeed in an excellent mood today.
It was not just because the Hogyoku—which he had spent a century perfecting at the cost of countless souls—was finally complete and about to display its true, boundary-breaking power today.
What brought him even more joy was the subject who would be undergoing the Arrancar experiment today...
The laboratory doors slowly slid open, responding to Aizen's Spiritual Pressure.
A putrid stench, mixed with the violent Spiritual Pressure of a Hollow, washed over them.
There was no precise machinery in this massive, circular laboratory, only a giant, bottomless pit.
At the bottom of the pit, a massive black lump of flesh, as large as a small hill, was writhing violently.
It was a Menos Grande of absurdly exaggerated proportions.
Its appearance resembled a giant worm covered in countless appendages and barbs, with dark red Spiritual Pressure flowing through the gaps of its horrifying carapace.
Its head had no eyes, only an abyssal maw lined with row upon row of razor-sharp teeth, looking as though it could devour anything.
And on its back grew several patterns resembling twisted, wailing human faces.
Gin Ichimaru looked at the monster in the pit and slightly raised an eyebrow. "My, no matter how many times I look at it, this fellow's appearance is truly disgusting to the extreme..."
"Lord Aizen, are you certain you want to make this giant bug one of us? It really is..."
"Do not be deceived by outward appearances, Gin," Aizen said, walking to the edge of the pit and looking down at the massive worm Hollow from above.
His eyes revealed a scholar-like appreciation. "Hidden within this ugly shell is a wondrous soul that has crossed the laws of space and time, witnessing the truths of two worlds."
Hearing Aizen's voice, the giant worm at the bottom of the pit ceased its frantic writhing.
It slowly raised its massive, eyeless head and let out a low, submissive hiss in Aizen's direction.
It was an entity more unique than any Hollow, more bizarre than any soul.
Zouken Matou, or rather, Makiri Zolgen.
To Zouken Matou, the fact that he had been reduced to this state—a form that even he found nauseating—was entirely an absurd and cruel joke of fate.
Deep within his consciousness, that nightmare-like scene was still deeply etched.
That day, in the Great Cavern beneath Ryuudou Temple, Zelretch had struck him down.
He remembered it vividly: accompanied by that iridescent light capable of severing causality and erasing existence, he had let out a scream of despair.
Zouken thought his existence would be completely stripped from the axis of time, bringing about his absolute end.
But a miracle—or perhaps a curse—befell him.
By sheer coincidence, he had planted the power known as Colorless into the otherworldly Soul Reaper named Asuka.
Although this power was ultimately broken, the wish-granting force within Asuka, capable of twisting reality, had invisibly entangled itself with his soul.
When Zelretch's Second Magic shattered his existence and banished him into the void...
This otherworldly thread entangled with Asuka acted like a lifesaving spider's silk, forcefully altering the trajectory of his fate from total erasure.
He was banished to the world Asuka hailed from.
However, due to the violent fluctuations of the space-time turbulence, the point in time he landed was decades earlier than when Asuka returned to this world.
Furthermore, his landing point was not the Soul Society he so deeply yearned for, brimming with Reishi and Soul Reapers, but rather this Hueco Mundo, a land filled with hunger and slaughter.
When Zouken Matou awoke in those cold white sands...
He was horrified to discover that his proud Magic Circuits had been completely destroyed, and his shoddy immortal body, sustained by worms, no longer existed.
He had become the lowest class of Hollow, an insectoid Hollow that didn't even possess a complete form.
And in Hueco Mundo, weakness meant being devoured.
To survive, and for the sake of his near-pathological obsession with immortality and the Root...
The once high-and-mighty magus discarded his last shred of human dignity.
Like a dog, he began to frantically gnaw on the remains of other weak Hollows in the white sand, slowly growing and developing.
Enduring the agony of his soul being torn apart, he devoured and fused with other Gillians, continuously marching down the path of evolution.
Finally, his perseverance paid off.
His soul underwent a severe mutation in Hueco Mundo's malicious Reishi environment. The concepts of his former worm magecraft combined with a Hollow's instincts, allowing him to evolve into an extremely hideous insectoid Menos Grande.
From a Gillian to an Adjuchas, he spent long years amidst endless slaughter and madness...
But just as he was on the verge of becoming a Vasto Lorde, preparing to establish his own insect empire in this wasteland...
He met the man who would change his fate.