Tier Harribel  

Now that Nnoitra had become an Arrancar, his power had increased tenfold. He was certain that if he encountered that female Vasto Lorde again, he would be able to defeat her. This time, he would show her the true meaning of "survival of the fittest"!

…

Inside Las Noches, Ailin opened his eyes, having completed his daily power enhancement.

Ulquiorra Cifer, the 4th Espada, stood silently below the throne, patiently awaiting his master's attention.

"Lord Aizen," Ulquiorra bowed his head slightly as Ailin opened his eyes.

"Ah, Ulquiorra. You sought me out directly. Have you found a suitable candidate for the Espada?"

"Yes, Lord Aizen."

"Oh?" Ailin leaned forward, intrigued. "Bring them forth, Ulquiorra. I am curious to see what kind of being has earned your approval."

With Ailin's permission, Ulquiorra turned and left the hall. He returned a short while later, accompanied by a massive caterpillar-like Hollow. The moment Ailin laid eyes on the creature, he knew it was Yammy Llargo, the 10th Espada—the only Espada whose rank could change upon releasing his Zanpakutō.

"Oi, Ulquiorra, you brought me here just to see this Shinigami?" The caterpillar Hollow trailed behind Ulquiorra as it entered the hall. As it looked up at Ailin, its anger flared. It reared its head high, making its already enormous body appear even more imposing.

"Yammy, this is Lord Aizen. Show some respect."

"Hah? Ulquiorra, you want me to address a Shinigami as 'Lord'?" Yammy lowered his head and glared at Ulquiorra. Seeing no reaction from his comrade, Yammy's rage intensified.

"Damn it, what did you do to Ulquiorra?"

"Oh?" Ailin chuckled at Yammy's accusation. "Why do you assume that I did something to Ulquiorra? Why not consider the possibility that he chose to follow me willingly?"

"That's ridiculous! You're a Shinigami, and we're Hollows! Why would a Hollow ever willingly follow a Shinigami?"

"How about a wager?" Ailin proposed. "If you still hold that belief after our conversation, I will grant you a fair fight. Defeat me, and you can take Ulquiorra back. However, if you change your mind, you must swear absolute loyalty to me and obey my commands. What do you say?"

Ailin knew that Yammy relished combat and craved bloodshed. Even after ascending to Arrancar and no longer needing human souls for sustenance or evolution, he had still used his "Soul Sucking" ability to devour countless humans in the World of the Living, causing widespread devastation.

However, Yammy possessed a quality that none of the other Espada had: loyalty.

Of course, this wasn't because he particularly admired Aizen. Yammy was a simple creature who preferred action over thought. Once he pledged allegiance to someone, he wouldn't betray them.

The other Espada had their own reasons for following Aizen.

Coyote Starrk, the 1st Espada, was driven by loneliness. In Las Noches, he found companions who could withstand his immense reiatsu.

Baraggan Louisenbairn, the 2nd Espada, had submitted to Aizen's overwhelming strength. After being decisively defeated, he was persuaded by Aizen's vision of conquering the Soul Society and agreed to relinquish Las Noches, becoming the second-ranked Espada.

Ulquiorra Cifer, the 4th Espada, sought to experience something beyond the "nothingness" that defined Hollow existence. Serving Aizen allowed him to witness things that transcended his limited understanding.

Nnoitra Gilga, the 5th Espada, craved to become the "strongest." Having achieved Arrancar status but failing to claim that title, he sought battles with those stronger than himself, hoping to die as a stepping stone for the true "strongest."

The other Espada had their own motivations as well.

Only Yammy Llargo possessed true loyalty.

"Hahaha, you're going to lose, Shinigami!" Yammy roared with laughter, refusing to believe he would ever submit to a Shinigami. "Be prepared to return Ulquiorra to me, or I'll crush you with my fists!"

"Is that so?" Ailin smirked. "I hope I can still hear those words from you later."

He extended his right hand, and a blue, glowing orb materialized—the half-formed Hōgyoku created by Aizen. With a thought, the Hōgyoku flew from his hand and hovered above Yammy. A beam of blue light descended, enveloping his entire body.

"Roar!" Yammy let out a deafening roar as the blue light washed over him. His massive body began to shrink, transforming from a multi-legged creature over ten meters long and two meters tall into a towering, muscular humanoid nearly three meters in height.

He had thick, dark red eyebrows, and his Hollow mask, now reduced to a jagged white bone structure, covered only his chin. A Zanpakutō appeared at his waist.

"What, what is this?" Yammy exclaimed, marveling at the sensation of moving in a humanoid body for the first time.

"This is Arrancar, a branch of the evolutionary path for Hollows," Ailin explained, catching the returning Hōgyoku in his hand. "Arrancar is a path distinct from the traditional Hollow evolution through devouring. Only Hollows of Adjuchas class and above are eligible to become Arrancar. As an Arrancar, you no longer need to fear regression, and you gain power far exceeding that of your previous form."

"Yammy Llargo, will you follow me and serve under my command? Or will you defy me and fight to reclaim Ulquiorra?"

Yammy pondered his options, overwhelmed by the power surging through his new body. He was impulsive but not foolish. He understood that a being capable of granting such immense power was not to be questioned. Even Ulquiorra, far more intelligent than him, had chosen to serve this Shinigami. There must be a reason.

"What was I saying again?"

After Yammy agreed to serve under him, Ailin personally branded him with the number "10," signifying his rank among the Espada. This wasn't the type of "10" that could transform into a "0" upon releasing his Zanpakutō.

While Yammy had undoubtedly grown stronger, surpassing Nnoitra in power, he still fell short of the top four Espada. Upon releasing his Zanpakutō, Yammy had declared that even Ulquiorra was now nothing more than trash in his eyes, just like Nnoitra and Grimmjow. His boast was reminiscent of Renji Abarai's claim during the Thousand-Year Blood War that he had reached a level where he could fight Aizen.

Based on his current performance, Yammy was far from deserving the title of "Cero Espada."

After all, despite his power, he was ultimately just an Adjuchas-class Arrancar. Even at his absolute limit, his strength would only rival Ulquiorra's first Resurrección.

With a wave of his hand, Ailin dismissed Ulquiorra and Yammy. Then, he activated his reiatsu sensing ability to its fullest extent.

"Yammy is in place. Now, where is Harribel?"

With his current reiatsu, Aizen's clone couldn't sense the entirety of Hueco Mundo. However, he possessed the most potent illusion-type Zanpakutō, Kyōka Suigetsu.

To Ailin, Kyōka Suigetsu was not only a perfect control-type Zanpakutō but also a powerful support tool. Its complete hypnosis could be used to enhance his own abilities as effectively as it could be used to deceive his enemies.

Using Kyōka Suigetsu, Ailin amplified his reiatsu sensing ability to the limit his clone could handle. In an instant, the entire expanse of Hueco Mundo appeared in his mind.

He quickly located Nnoitra's reiatsu signature. Nearby, he sensed four other Hollow reiatsu signatures - one strong and three weaker ones.

"Could that powerful reiatsu belong to Tier Harribel?"

Following his instincts, Ailin vanished from Las Noches and flew towards those reiatsu signatures.

…

The ground of Hueco Mundo was covered in yellow sand, the remnants of countless Hollows. Mountains and rocks were rare sights. Even rarer was water.

Yet, in this desolate landscape, there existed a towering cliff face and a half-formed lake. Occasionally, Hollows would visit this lake to quench their thirst before moving on.

All the Hollows who came here behaved respectfully, refraining from causing any trouble. They knew that everything here belonged to a powerful being who had graciously allowed them to drink from this lake. It was a rare act of kindness in the harsh world of Hueco Mundo.

The name of this powerful being was Tier Harribel. She was a renowned Vasto Lorde-class Hollow. Even during the reign of Baraggan Louisenbairn, the self-proclaimed King of Hueco Mundo, he had invited Harribel to join his court.

However, Harribel found Baraggan's methods and treatment of his subordinates repulsive and repeatedly refused his offer.

If she hadn't been one of the few Vasto Lordes in Hueco Mundo, Baraggan would have long since sent his forces to eliminate her.

As a result, despite not actively building a faction, Harribel had attracted a following of Hollows who had chosen to gather under her protection. Over time, other powerful Hollows who refused to submit to Baraggan sought refuge with Harribel, forming a loose alliance that rivaled Las Noches in strength.

One day, a Hollow with a disc-shaped collar and a crescent moon staff arrived at Harribel's domain.