The sealing technique deep within Muken was clearly connected in some way to the sealing technique in Hell.
Whenever the seal in Hell absorbed Hell Reishi, some of that Hell Reishi would overflow here.
Moreover, Nanatsuki observed that the Hell Reishi was being purified—its hellish aura stripped away—and converted into blue Reishi.
These purified blue Reishi then gathered on the pedestal of the sealing formation and were stored within countless spiritual threads.
The very walls of this space were covered in these Reishi threads.
"Hell-tainted Reishi is being transformed into normal Reishi here..." Nanatsuki narrowed his eyes.
Saitō Furaofushi, still speaking with her grandmother through the conch communicator, was likewise stunned by the vast amount of Reishi flowing through the spiritual threads.
"If you used the Reishi stored here to fire a Kidō Cannon, it might be enough to obliterate the entire Seireitei!" she exclaimed.
The "Kidō Cannon" she mentioned was one of the Tenshihō Banshōban, massive Kidō-based divine weapons that required many highly skilled Shinigami to operate.
"If I'm right, the sealing technique on the Hell side is linked to this one. These Reishi are likely used to sustain that seal," Nanatsuki said.
Over in Hell, the sealing formation disassembled everything sucked into the vortex into Reishi. The Hell-tainted Reishi was then transmitted here, stripped of its hellish aura, converted into standard Reishi, and stored in the network of spiritual threads.
As with any spellcraft based on Reishi, continued function required an ongoing supply—and this seal drew from the Reishi stored in the threads to remain active.
"The stripped hellish aura is condensing into a single orb," Nanatsuki noted as his gaze fell on the pedestal beneath the glowing seal, where a black-and-red orb had formed.
The pure Hell aura extracted from the Reishi had gathered into Hell Miasma, and this miasma was being absorbed by the black-red orb.
Hell Miasma was a visible manifestation of highly concentrated Hell aura.
It could also be seen during soul funerals or when the Gate of Hell opened.
Hell Miasma had a powerful attraction to Reishi. When it contacted ambient Reishi, it easily corrupted it into Hell-tainted Reishi. That's why Hell Miasma rarely lasted long in the Three Realms.
But in this place, not only was it persisting—it had even condensed into a tangible orb.
That was because all the Reishi floating in the air here were already Hell-tainted; all the regular Reishi had been sucked into the sealing formation's spiritual network.
If not for the Reishi stored in the threads, once the seal finished purifying all the Hell Reishi, this entire space would become a Reishi vacuum.
The pedestal beneath the seal had such a strong Reishi absorption ability that it was even pulling in the faint Reishi naturally released from Nanatsuki and Furaofushi's breaths.
From the conch communicator came Saitō Seiko's voice:
"An orb condensed from Hell Miasma? I can't believe you managed to see one in the Soul Society. Even in Hell, such things are incredibly rare. We call them Hell Pearls, and they can only be found in areas with the most intense concentrations of Hell aura. If one appeared in Hell, it would cause a scramble among the wicked souls."
"People fight over them?" Nanatsuki asked, intrigued. "What do they do?"
Saitō Seiko explained,
"Those who fall into Hell don't truly die—not until their minds are completely assimilated. Even if their spirit body is destroyed, they can potentially regenerate."
"The key lies in the Hell Miasma."
"If the spirit body is destroyed, Hell Miasma will gather Reishi and restore the body. But since the ambient Hell Miasma is so thin, the process is slow."
"But with a Hell Pearl, the high-density Miasma it contains can restore a broken spirit body almost instantly."
Nanatsuki understood: to the damned, a Hell Pearl was like a resurrection coin.
He remembered when Yamamoto Genryūsai Shigekuni defeated Nobutsuna Shigyō, who had returned from Hell. Even then, Shigyō had said that being killed only meant going back to Hell—it didn't mean disappearing.
It made sense now. After Shigyō's spirit and Reishi returned to Hell, the Hell Miasma would begin reconstructing his spirit body.
Nanatsuki asked, "So... does the Hell Pearl have no effect on spirit bodies from the Three Realms?"
Saitō Seiko replied,
"Not entirely useless. Hell Miasma has a powerful affinity for Reishi."
"The stray traces of Miasma that float out during Soul Funeral Ceremonies or when the Gate of Hell opens aren't a big deal."
"But a Hell Pearl—formed from extremely concentrated Miasma—if unleashed, it could draw out the Reishi from a spirit body. That would cause serious damage."
"You could use it as an assassination tool."
"Sounds effective..." Nanatsuki muttered, stroking his chin. "If enough Miasma is released, it could literally collapse the spirit body. But how would I even collect the Pearl? Wouldn't I get my Reishi drained just by touching it?"
"Do you have any Sekkiseki?" asked Saitō Seiko. "It can block Reishi. Use it to make a container, and the Hell Miasma won't be able to drain your energy."
Nanatsuki happened to have Sekkiseki ore stored away and had already saved up a fair amount. He took a chunk of it out.
Though Sekkiseki wasn't particularly hard, it had the perfect Reishi-blocking properties. After a few minutes of work, he had crafted a small square box.
He used it to store the Hell Pearl safely.
This trip had been fruitful—uncovering secrets about the Soul Society's connection to Hell and obtaining a Hell Pearl.
This particular pearl had spent years in Muken absorbing the Miasma from the sealing formation. The amount of Hell aura it contained was overwhelming—enough to possibly annihilate even captain-class Shinigami if unleashed.
The seal here was far too complex. Nanatsuki couldn't decipher it with his Kidō knowledge. Even if he could brute-force it open, he didn't dare.
His instincts warned that forcefully breaking this seal would have catastrophic consequences.
Given that this sealing technique spanned across realms, whatever it was containing couldn't be ordinary.
Nanatsuki had a suspicion: that the eye they'd seen might be a remnant of the Lord of Hell, the one defeated by the Soul King long ago.
And now, with the Soul King acting as the keystone stabilizing the World of the Living, the Soul Society, and Hueco Mundo—if the Lord of Hell were to awaken prematurely, there was no guarantee the Three Realms could survive the crisis.