This honestly wasn't a grand feat.
Ichigo and his friends managed to enter this realm with the help of Kisuke Urahara. Then there were Aizen and the Quincies, who had somehow opened a portal here.
These things were never explained in terms of how they accomplished them, but with spells and methods of teleportation, it wasn't hard to believe. Now that Silas had become one of the select few to do the same, his ambitions could be further expanded.
The sands of Hueco Mundo shifted beneath his shoes as he journeyed on foot.
Days had blurred into weeks, each marked by how hungry the Hōgyoku inside him was getting. To tell days apart from nights was not possible in Hueco Mundo without something special.
Silas had left the desolate outskirts far behind, venturing deeper into this realm. Each step was guided not by maps or instincts, but by the raw pulse of his spiritual pressure. He would, at times, feel lesser Hollows gathered in one area. But none of them intrigued him enough to communicate with.
His target was not merely any Hollow. This journey was a hunt for power—for a prize that would further his goals. He sought a 'Great Hollow" also known as a "Vasto lorde".
These apex predators of Hueco Mundo were rare; their forms were almost like a man's, and their power dwarfed that of lesser Hollows. And somewhere, amid the shifting sands and bleached bones of this realm, one such creature resided.
Silas knew the name, deeming this Hollow as one of the strongest Hollows in Bleach: Coyote Starrk.
Hollows were categorized by their class. They ranged from Hollows to Gillians to Adjuchas to Great Hollows.
Hollows are newly born creatures that make up for all corrupt Souls. But what happens to that Hollow when they've fulfilled their purpose in the world of the living? They have the potential to become Gillians, also known as Menos Grandes.
These creatures are huge monsters of at least two to six stories tall, easily dwarfing lesser Hollows. They possess white masks with elongated noses and thin spikes framing their necks. Their cloaked bodies conceal large, clawed hands and pointed feet, while their appearance and abilities alone are designed for breaking the masks of fellow Hollows.
While most Gillians are mindless and dangerous, the dominant Hollow within them occasionally gains control, as reflected in the creature's unique mask. These variants can evolve into Adjuchas through continued cannibalization of other Hollows, including their fellow Gillians.
Adjuchas, smaller and rarer than Gillians, are significantly smarter and stronger, capable of leading Gillians into battle and even challenging captain-level Soul Reaper captains with their power. In terms of appearance, they can range from bulky to animalistic.
Adjuchas are rare because few individual Hollows can dominate the others within a Gillian to achieve this form. To maintain their status, Adjuchas must continually devour other Hollows or risk their minds being subsumed and reverting into a Gillian again.
If even a part of an Adjuchas is devoured, their evolution is permanently halted, though they will no longer revert to a Gillian form.
Finally, there was the rarest and most evolved form of Menos, a Great Hollow. They were so few that their entire population within Hueco Mundo can be counted on one's own hands.
Their power allegedly surpasses that of captains in the Seireitei, and they are surprisingly small, roughly the size of a man. While Great Hollows are known for their cero and sonído skills, the process by which they evolve has never been revealed.
Grimmjow Jaegerjaquez, a Hollow who was the rival of Ichigo Kurosaki, theorized that consuming large numbers of Hollows could transform an Adjuchas into a Great Hollow. But Shawlong Koufang, his subordinate, proved this ineffective.
With these things in mind, one needed to question: which class was Coyote Starrk in that would pique the interest of Silas?
A Great Hollow!
Tōshirō Hitsugaya was stated to have feared that Aizen, having obtained ten or more Great Hollows with Soul Reaper abilities (known as "Arrancars"), would cause the downfall of the Soul Society.
This is exactly what Silas was planning. Only, instead of creating these ten Arrancars, known as "Espadas", he was going to fashion them in a manner that would utterly destroy all three worlds!
In Bleach, there existed several of these Great Hollows, most of whom were turned into Arrancars to help amplify their powers.
When turned into an Arrancar, they gained a Zanpakutō. This Zanpakutō wasn't like that of a Soul Reaper's. Instead of a Bankai, they used a "resurrección", a means of releasing the core of an Arracnar's ability that was sealed within their weapon. After its release, regain their original powers from their Hollow forms.
The most powerful of the Arrancars was never accurately clarified. Aizen form the top ten most dominant ones by labeling them with numbers zero through nine.
The Arrancar, who was number one, was deemed the strongest Hollow amongst the Espada—so it was believed. This was redacted, in which the numbers were assigned based on the time of birth of an Arrancar. However, this was a problem because Coyote Starrk was ranked number one.
He was one of the last Hollows to join the ranks of an Espada.
Silas knew in what order Arrancars would be formed (via the Hōgyoku), as well as which ones would join the Espada.
Starrk, being one of the last members, wasn't recruited until after Aizen left the Soul Society. That meant that Silas would have more than the right to interact with that Great Hollow. His only problem was finding him. Hueco Mundo was a vast territory, seeping with sand and emptiness.
Finding him was not simple serendipity.
But with his refined senses, honed by spiritual awareness far beyond that of any Soul Reaper, Silas eventually felt the faintest tremors of someone's presence, more powerful than the other Hollows.
It was a beacon piercing the spiritual cacophony of Hueco Mundo, a pulse both potent and strangely lonely. This was no mere beast, but a creature trapped by its own power, isolated within its desolate kingdom.
Yet the question still lied: was it Coyote Starrk?