After completing stabilization of the perfected Hōgyoku, Kurotsuki Renya began advancing the next phase of evolution within his ranks.
The first to undergo full boundary integration was Nelliel Tu Odelschwanck.
Unlike ordinary Arrancarization which merely removes the Hollow mask and grants partial Shinigami attributes this process dissolved the final instability between Hollow essence and Shinigami structure.
When Nelliel completed the procedure, the antelope-like mask fragment upon her head receded completely. In its place remained two subtle, curved horns formed from condensed spiritual structure rather than residual mask matter. The white Hollow armor that once reinforced her forearms dissolved into pure reishi and did not reform.
Most notably
Her Zanpakutō vanished.
Not destroyed.
Integrated.
Her spiritual pressure no longer required external manifestation in blade form. The weapon had become intrinsic.
Grimmjow Jaegerjaquez followed.
Upon stabilization, the mask fragment that once rested along his jawline and later shifted to his forehead during Resurrección disappeared entirely. The hardened skeletal plating that defined his Panthera state no longer manifested as external armor.
Instead, faint black fur traced across portions of his arms and shoulders subtle, controlled, predatory. His Reiatsu sharpened rather than expanded recklessly. The feral instability that once defined his Hollow core had been tempered into lethal focus.
Then came Tier Harribel.
Her transformation was the most visually dramatic.
The Hollow armor that once covered her torso and jaw dissolved completely. In its place, streamlined aquatic traits manifested fine scale patterning across her skin, faint gill-like structures along her cheeks, subtle fin ridges forming at her forearms and calves. A narrow dorsal fin ridge extended down her spine, composed not of bone, but compressed reishi.
Her Zanpakutō likewise disappeared.
Integrated.
No external blade.
Only presence.
Renya observed carefully.
Two consistent characteristics emerged from complete integration:
First:
External weapons ceased to exist as separate entities. The Zanpakutō became internalized no longer a conduit, but an extension of being itself.
Second:
Animalistic traits refined rather than dominated. Each Arrancar retained a humanoid foundation but expressed the pure archetype of their Hollow origin.
Ulquiorra — bat
Perez — hyena
Nelliel — antelope
Harribel — shark
Grimmjow — panther
The grotesque remnants of Hollow masks were gone.
What remained was distilled identity.
However
Renya did not mistake this for transcendence beyond Shinigami.
Integration did not automatically elevate them to the level of Yamamoto Genryūsai or transcendent Aizen.
It removed instability.
It refined Reiatsu density.
It granted evolutionary continuity.
Ulquiorra, even before this process, possessed the capacity to overwhelm Bankai Ichigo in their encounter at Las Noches. His Segunda Etapa placed him solidly in high Captain-tier combat power.
Harribel and Nelliel, after integration, stabilized at comparable levels
Captain-class without question.
Grimmjow trailed slightly behind, yet remained firmly within Captain-tier thresholds.
Perez approached the lower boundary of that classification.
Renya then turned his attention to another group.
The Fullbringers.
Unlike Arrancar, Fullbringers manipulate the souls of matter through Hollow-tainted lineage. Their power structure differs fundamentally from both Shinigami and Hollow systems.
Complete Hollowfication for them required careful modulation.
Tristan's form stabilized into an avian Hollow
crane-like in silhouette, elongated beak structure formed of hardened reishi, legs reinforced with blade-edged armor. His Fullbring affinity for velocity manifested in extreme lower-body reinforcement.
Tsukishima Shūkurō transformed into a massive serpentine Hollow his torso elongated into scaled coils, cold spiritual pressure radiating outward in constricting waves. His capacity to "insert presence" metaphorically manifested as territorial dominance within his Reiatsu field.
Giriko and Yukio were not candidates; instability risks were excessive.
Kūgo Ginjo underwent the most violent transformation.
Upon total Hollow integration, his Fullbring cross dissolved into his chest. His body expanded into a massive bull-like structure, two horns formed from condensed black reishi spiraling from his temples. His blade did not manifest externally his horns themselves functioned as primary spiritual weapons.
Unlike Arrancar integration, the Fullbringers' complete Hollowfication produced two distinct effects:
First:
Bestial dominance replaced humanoid balance.
Second:
Their original Fullbring affinity became hyper-concentrated rather than diversified.
Ginjo's absorption-type combat style became direct impact force.
Tsukishima's presence-manipulation translated into oppressive Reiatsu territory control.
Tristan's speed became bladed acceleration.
After dual-stage enhancement Hōgyoku integration layered upon Fullbring core amplification their power increased dramatically.
Tristan and Tsukishima reached stable Captain-tier output.
Ginjo exceeded that baseline.
Renya evaluated silently.
He now possessed:
Ulquiorra (high Captain-tier, Segunda Etapa precedent)
Harribel (Captain-tier stabilized)
Nelliel (Captain-tier stabilized)
Grimmjow (Captain-tier lower range)
Ginjo (Captain-tier upper range)
Tsukishima (Captain-tier lower range)
Perez (approaching Captain-tier)
Seven viable Captain-class combatants.
Yet Renya was not naïve.
In the Thousand-Year Blood War, Captain-tier combat power was no longer rare.
Yamamoto Genryūsai — overwhelming anomaly
Unohana Retsu — hidden monster
Kyōraku Shunsui — strategic apex combatant
Adult Hitsugaya Tōshirō — post-maturation spike
Zaraki Kenpachi, after unlocking his sealed potential.
Renji Abarai post–Royal Palace training.
Byakuya Kuchiki after Ōken rehabilitation.
Rukia Kuchiki after mastering Hakka no Togame.
Each demonstrated Captain-level lethality against Sternritter elites.
Add to that:
Kisuke Urahara
Yoruichi Shihōin
Isshin Kurosaki
Ichigo Kurosaki
Captain-tier was a threshold
Not supremacy.
Renya did not expect his forces to dominate the Wandenreich.
But survivability?
Yes.
That objective had been achieved.
Which left his original purpose in Hueco Mundo.
…
Outside Las Noches, beneath the vast white moon, Renya stood alone in the desert.
Before him gathered:
Ulquiorra.
Harribel.
Nelliel.
Ginjo.
Tsukishima.
Nelliel yawned lightly.
"You summoned us this far from Las Noches for what purpose?"
Renya's voice was calm.
"I require combat stimulus. You will attack me with full force."
Ginjo frowned.
"All of us?"
"Yes."
Harribel's gaze sharpened.
"The five of us simultaneously, in our highest states, could rival pre-transcendent Aizen."
Renya did not deny it.
Captain-tier Reiatsu, when compounded, was lethal.
He smiled faintly.
"Then consider this your opportunity."
Ginjo exhaled slowly.
"You are certain?"
Renya met his eyes.
"If I fall, you are free."
A brief silence.
Ginjo shook his head.
"I have no desire to see you die."
"You cannot kill me," Renya replied evenly. "Release everything. Segunda Etapa. Complete Hollowfication. No restraint."
Ginjo closed his eyes.
"Understood."
Reiatsu detonated outward.
His body expanded into the massive bull-shaped Hollow form, black spiritual pressure rolling across the sand like a stormfront.
Simultaneously
Ulquiorra ascended into Segunda Etapa, black wings unfolding against the moonlight.
Harribel's integrated shark-form manifested in refined aquatic predation.
Nelliel's antelope silhouette sharpened into elegant lethality.
Tsukishima's serpentine mass coiled across the desert floor.
Five Captain-tier combatants.
Reiatsu distorted the air.
Sand lifted from the ground in spiraling currents.
Renya inhaled once.
Then spoke quietly:
"Bankai."
The desert trembled.
"Nine Heavens Resounding Thunder — Universal Heavenly Sovereign."
Lightning split the white sky.
And the battle began.