The moment a shinigami obtained a zanpakuto, his path to power became determined.
The first step was to enter the inner world of the Zanpakuto and communicate with the sword and know its name. Once this was done, the shinigami would have access to the power known as Shikai, or first release. This was the step that blocked 80 to 90% of shinigami. Most shinigami died without ever knowing the name of their swords.
In the same way, those who did manage to reach the level of Shikai stopped being seen as cannon fodder and could reach the rank of a seated officer. From that moment on, they would dedicate their training toward better understanding the abilities of their Shikai.
But, this wasn't the end. There was another level, one known as Bankai. A level that only a select few ever managed to reach despite years and years of training. In any generation, it was rare for the number of Bankai holders to even reach fifteen out of more than six thousand shinigami.
This went to show just how low the rates were.
The Bankai was a qualitative upgrade. A fundamental change that could increase more than 10 times the power of its wielder. To achieve it, one must be able to materialize and subjugate their Zanpakutō spirit.
Materialization meant the opposite of getting dragged into the Zanpakutō's inner world, that is the wielder needs to summon the Zanpakutō's spirit into the physical world. It usually takes 10 years or more to achieve, plus the experience needed to master.
The abilities bestowed by a Bankai differed. Most of the time, like with Byakuya for example, they only increased the power of the skills already owned by the Shikai. Some other times, like with Soi Fon, the Bankai took an opposite route.
Gojo did not exactly know all of what his Bankai could do. But, the passive abilities of his Bankai were already enough to give him a headache and that, quite literally.
For the hollows, the moment they saw Gojo appear in the fray, most of them began to rush to attack him without thinking much about the situation. But a few smarter ones, such as the panther hollow immediately sensed a huge danger and began to run away.
Grimmjow was a proud warrior. Normally, he would never consider fleeing even if it meant death. But, the very moment that man appeared, for the first time since he gained consciousness, Grimmjow felt afraid.
Was it perhaps because he had the instincts of a beast? He would never know the answer.
But, at the sight of this man, all thought about staying vanished from his mind and only one thought kept screaming at him.
Run for your life.
Don't wait. Don't look back. Don't even think.
All he could think of was running away as fast as possible, and that he did.
This was what saved his life.
Screaming at his partner to follow him, he began to run at a speed he never even thought was possible to reach.
He did not know how long he ran. But, when his instincts finally calmed down, when he finally stopped running, when he finally turned back with only two out of his five companions not far behind him to observe what he had run away from.
Grimmjow opened his mouth wide open and felt his legs give under him. What he was seeing was simply too much of a shock.
He muttered hoarsely. His mind was unable to process what he was seeing for one simple reason.
There was nothing to see. All the hollows had simply vanished.
Refusing to accept what he saw, he stretched his senses as far as he could, trying to feel the slightest Reiatsu presence of a hollow.
But, there was nothing.
In the instant, it took him to run away.
In a moment that could not even have lasted more than a few minutes.
In that short span of time...Nearly two thousand made of a mix between Gillians and Adjuchas had been utterly annihilated.
[A few moments ago]
"Well, then… Bankai!"
The moment Gojo uttered this word, the world seemed to fall silent, before everything began to tremble.
A flash of light momentarily blinded all those present, but once the light vanished, they were left speechless at the sight that was presented to them.
Gojo was currently sitting on a regal throne dyed in silver. The motifs of lions were delicately curved on the front of the handles of the golden throne.
An aesthetically cracked pattern dyed in gold, along the cracks, was etched on the headrest of the throne giving it an imposing presence taking the form of a black sun.
It was a throne oozing authority and power.
Meanwhile, Gojo's attire consisted of a silvery-white and black accented ceremonial buttoned-up suit, accents of gold-lined along with the collars and the strip of his suit, its buttons were a mixture of gold and silvery-white. His hands were covered up to his forearms with silvery-white gloves while he wore thigh-high boots of the same color.
A shawl draped over his left shoulder and ended at his right upper arm as Gojo indifferently stared ahead with his head resting on the knuckles of his left hand and his right leg crossed over his left in an arrogant sitting position. The handle of his zanpakuto rested loosely in his right hand as he held it upside down with his outstretched right arm.
Next to him, sitting on a second throne was none other than Kogo, but this time, rather than looking like a middle schooler, she looked more like a mature woman. Be it her throne or her clothes, they were nearly in all points similar to those of Gojo.
The difference rested on the fact that her clothes and throne, rather than a bright silver-white like those of Gojo, were of a deep black, reminiscent of the darkness of the night.
Her suit and skirt accentuated her beautiful and bountiful forms, and where there was a black sun etched on Gojo's throne, a silver moon was etched on her.
Two thrones, two colors, one Kingdom. One represents the light and the other the darkness. One of the Moon and the other the Sun.
"Bankai: Tengoku futago no Gyokuza"
Sitting on the throne as he observed all the hollows cowering in front of him, Gojo did not feel any joy.
In fact, he could barely focus on the scene ahead of him. After all, currently, he felt as if his head was about to explode.
One of the passive effects of his zanpakuto, aside from the absorption of Reishi, was the near-omniscient viewpoint in a domain.
When he used his Shikai, that zone was 10 meters but the range of his Bankai was frighteningly huge — Fifty kilometers.
Without a doubt, in all the history of the soul society, this was the largest domain type Bankai in existence.
But for Gojo, this was like a curse. The worst was, fifty kilometers was far from being the limit.
The third passive skill of his zanpakuto, one that was exclusive to his Bankai, was that the zone he covered could grow.
The longer his Bankai stayed activated, the larger the zone he covered became. Like a kingdom slowly growing as it conquered everything in its wake.
The amount of information that filled his mind was simply overwhelming. Had it been his human self, reverse cursed techniques or not, he would have died after his brain exploded.
'Thankfully, Garganta is void and the amount of Reishi is low. This greatly diminished the amount of information and the gathering speed of said information.'
The first time he used his Bankai in Soul Society, he thought that he was about to die a second time.
Bearing through the pain caused, he focused on the thousands of hollow and waved his hand,
For Soi Fon, what happened next felt like she was hallucinating.
When Gojo waved his hand, she felt sick. As if her body was being pulled apart. As if something was trying to reduce her to nothing. She managed to fight back that feeling quite easily, but she never wanted to feel something like this ever.
As for the army of hollows that was standing, she could see them thrashing and screaming as their bodies slowly transformed into particles of light and vanished.
It didn't matter how much they tried to fight back, it did not matter how much they tried to escape. In the end, all of them vanished from the world. As if they had never existed in the first place.
Watching this scene, even though Soi Fon had seen hundreds of atrocities and escaped from the jaws of death an immeasurable number of times, she felt like her heart was about to come out of her throat.
When she realized that what happened to those hollows could have happened to her, goosebumps covered her body.
She now understood why Gojo had asked her to not kill him as a favor.
This kind of power simply broke through all common sense and there was nothing more frightening than the unknown.
Once all the Hollows dumb enough to not flee the moment he appeared died, Gojo immediately stopped his Bankai.
Already, blood was flowing out from his eyes and noses. Clearly, the stress he had been put through was out of this world.
'I am using it wrong.'
Standing up with the help of Nemu, Gojo thought inwardly with frustration.
Even now, he could feel it. This Bankai was lacking. It was as if an important piece of it was missing.
That was one of the reasons he never really considered himself as having reached the Bankai, for what he could currently do was nothing more than a mockery of what he should have been able to do.
From what he understood, his Bankai worked like Domain Expansion. By bringing out the inner world of Kogo, he could project it in the real world and trap his enemies in it.
But there was one thing that he was lacking—Walls.
His Bankai covered a wide zone, but nothing stopped things from entering or exiting.
A kingdom without any defense was nothing more than an empty castle.
Tengoku brought him the power of an army, but during a siege, the most appreciated and necessary defense was a wall.
A wall that could stop all attacks and he knew exactly what kind of wall he needed.
: Twin's Throne of Heaven.
(AN: Heh, I think I traumatized Grimmjow for life. Anyway, I think I have been pretty obvious about what is lacking in his Bankai. His Shikai activation doesn't use the pronom We for nothing you know? It's teamwork and he needs to bring his part to make it work.)