The impact from beyond the passage travelled through the black growth covering the chamber walls, and every strand tightened at once.
Rayleigh watched the contraction sweep past his boots and vanish into the tunnel ahead, where dozens of separate veins had converged so densely that almost none of the Dungeon stone beneath them remained visible.
A second impact followed before the first vibration had fully faded, noticeably closer this time.
Asfi crouched beside the nearest strand.
The faint red glow beneath its surface brightened with the impact.
"Whatever's on the other side knows we're here. The signal changed the moment we entered this chamber. Before, it was travelling deeper. Now the whole network is carrying it back toward us."
Tsubaki drew Tobiume but left it sealed.
"So much for sneaking up on it."
"We stopped sneaking several explosions ago."
"That wasn't my fault."
Asfi glanced at the scorch marks still visible on Tsubaki's armor.
"I wasn't assigning blame."
"You were thinking it."
Rayleigh headed into the passage before the argument could develop any further.
"Save it. If these veins carry information in both directions, then anything we do around them may be giving whatever's ahead more to work with."
That was enough to quiet them. The others followed him into the tunnel.
...
The growth thickened steadily as they descended.
Narrow strands embedded in the walls became cords, then bundles wider than Rayleigh's arm, forcing themselves through cracks the Dungeon was constantly trying to seal.
Pale new stone had formed along their edges in repeated layers, only to split apart whenever the black tissue expanded again.
Lyra walked near the rear with one hand resting on Arachne's hilt, looking up at the dark bundles winding through the ceiling.
"This really does look like something crawled inside the Dungeon and started growing through it."
Ardi kept Nejibana ready beside her.
"The Dungeon hasn't attacked it directly."
"We don't know that."
Rayleigh slowed beside a section where fresh stone had nearly buried one of the thinner strands and ran Benihime's tip lightly over the pale mineral.
"The Dungeon's answer to damage is usually more stone or more monsters. If this thing can consume both, trying to bury it may be the only response it has."
Asfi continued studying the walls as they moved.
"That could explain the missing magic stones too. If the growth takes them before the Dungeon can reclaim the remains, then whatever it normally recovers from dead monsters is being stolen first."
Rayleigh looked over.
"You think that's why the surrounding floors have been acting strangely?"
"I think taking thousands of magic stones from a living labyrinth is unlikely to be harmless. Beyond that, I'd rather see the source before I start inventing theories."
Ais stopped.
Everyone behind her stopped with her.
"What?"
Her eyes remained on the wall to their right.
"Inside."
Rayleigh sensed it a heartbeat later: something moving through the stone.
He shoved Asfi aside just as the wall burst outward.
A narrow grey creature tore through the Dungeon rock with both arms crossed over its head.
Black growth wrapped around its torso like an extra layer of muscle, with several strands disappearing into the broken wall behind it.
It landed between Rayleigh and Tsubaki but did not attack immediately.
Its body jerked once as the strands along its back tightened, and then its head turned toward Asfi.
The monster lunged.
Tsubaki stepped in and smashed sealed Tobiume across its side before it could reach Asfi.
The blow sent the creature into the opposite wall, but it twisted in midair and landed cleanly on both feet.
Then its posture changed.
One arm came forward while the other guarded its torso in a stance Rayleigh recognized from Anakitty.
Before anyone could react, the creature shifted again, borrowing Raul's posture, then Ais's, cycling through each almost as soon as it settled into it.
Lyra's expression tightened.
"It's going through everything they collected."
A pulse travelled down the black strand attached to its back, and the creature immediately changed again.
Tsubaki's eyes narrowed.
This time it had chosen her.
"That's irritating."
The monster drove forward with the same heavy step she favored whenever she intended to run straight through an opponent instead of wasting time outmaneuvering them.
Tsubaki let it commit.
Then she simply moved aside.
The copied momentum carried the creature past her, and Tobiume came down across its back.
The blade struck the black strand rather than flesh and nearly severed it.
The creature convulsed.
Its stance vanished at once. Whatever precision had guided its movements disappeared with it, leaving the monster to whirl around with claws out and mouth open like any ordinary Dungeon beast.
Rayleigh crossed the distance and cut through its chest.
The magic stone shattered, and the body dissolved.
The black strand remained.
It recoiled into the broken wall so quickly that Asfi barely had time to track it.
"That answers one question."
"The network isn't just passing along orders," Rayleigh said.
"No. It's choosing for them in real time. That monster wasn't deciding which technique suited the situation. Something else was making the decision and feeding it the answer."
Ais stared at the hole in the wall.
"The student had to think."
Asfi nodded.
"Yes."
Rayleigh started to sheath Benihime, then reconsidered and left it drawn.
"This one didn't."
The earlier Enhanced Species had learned, adapted, and made mistakes on their own. This creature had not needed to understand anything.
As long as the strand remained intact, whatever waited farther below could fight through it directly.
...
Three more attacked before the tunnel ended.
The first dropped from the ceiling and immediately demonstrated that the network remembered Arachne.
Instead of blundering into the points Lyra normally used to anchor her silk, it avoided them before she had even begun setting the trap.
Lyra noticed and adjusted without comment.
"Weave the net, Arachne!"
The short sword dissolved into black gauntlets around her hands and forearms, and nearly invisible silk spread through the narrow passage.
Rather than attaching the first strands to the monster, she fixed them to two loose pieces of Dungeon stone.
The creature avoided both.
Lyra grinned and pulled.
The two chunks tore free from the walls and swung inward from opposite directions, crushing the monster between them.
The strand attached to its back tightened, trying to drag the trapped creature free.
Instead of stopping it, Lyra looped Arachne's silk around the black growth.
Spiritual pressure immediately began draining through the thread.
She gritted her teeth and held on just long enough for the toxin coating Arachne's silk to enter the strand.
The reaction was small but obvious. The black tissue spasmed, and its attempt to retreat became uneven.
Rayleigh saw it too.
"Arachne's poison works on it."
"Somewhat." Lyra cut the thread before the drain could travel any farther. "Whatever passes for a nervous system in that stuff isn't normal, but the poison definitely scrambled something."
The creature pinned beneath the stones stopped coordinating its movements.
Ardi stepped in and drove Nejibana physically through its core.
The second attacker burst through the floor and tried to use short bursts of stolen water against Ardi.
She refused to answer with water of her own.
"Rankle the Seas and the Skies, Nejibana!"
The released Zanpakutō became a massive trident, and Ardi used its reach to keep the creature outside clawing distance.
Each strike went toward the strand connecting it to the floor rather than the monster itself.
When the creature tried to pull away, she changed her grip, hooked one of Nejibana's side blades around the damaged section, and released a single compact burst of water directly into the opening she had already made.
The pressure tore the strand apart.
The monster's coordination disappeared instantly.
Tsubaki destroyed its magic stone before it recovered.
The third attacker never made it out of the wall.
Asfi saw the stone beginning to bulge and placed an explosive directly over the point where the controlling strand was approaching the surface.
"Back."
The charge detonated.
The wall burst open, and a half-formed monster fell out with its controlling strand already severed.
It thrashed blindly until Ais stepped forward and broke its magic stone with one thrust from sealed Gonryōmaru.
By then, they had enough information to stop experimenting.
The strands could move or produce monsters through the walls and direct them while they fought. Cutting the connection stripped away that coordination.
Arachne's toxin interfered with the network, while ordinary physical damage worked perfectly well as long as they avoided giving the growth prolonged access to spiritual pressure.
Useful information, though Rayleigh doubted they had learned it privately.
If the source truly saw through its creations, then it had watched them discover every weakness.
The tunnel widened ahead.
At the same moment, the pull against Rayleigh's Zanpakutō intensified sharply.
He stopped.
"So this is it."
Ais came to stand beside him, and Gonryōmaru gave a low crackle inside its sheath.
Tsubaki rested Tobiume across one shoulder while Asfi moved toward the front and studied the opening before committing herself.
The tunnel ended roughly ten meters farther on.
Beyond it lay the source.
...
The cavern was enormous, though it was difficult to tell where its original walls had been.
Black growth covered almost every surface and converged around a huge organic structure embedded in the far side of the chamber.
Thick root-like masses wrapped around a swollen central body whose translucent flesh was filled with floating magic stones.
Thousands of them.
Some remained intact. Others had already been broken down into glowing fragments that drifted through branching channels in the tissue.
Every vein they had followed through the floor originated here.
Dozens spread from the central body and disappeared into the Dungeon walls, though three roots were far larger than the rest.
Each plunged into a different section of the cavern and pulsed hard enough to send faint tremors through the floor.
Asfi said nothing for several seconds.
Neither did Rayleigh.
There was no obvious head, no limbs, and no single core waiting to be shattered. The creature had not merely made a nest inside the Dungeon. It had grown into it.
Rows of translucent sacs surrounded the lower half of the central body.
Something moved inside them.
Lyra leaned forward slightly.
"Those are monsters."
Some were barely developed, with unfinished limbs and soft, incomplete armor.
Others already had weapons or defensive plates fused into their bodies before they had even emerged.
One cocoon held a narrow creature whose back was lined with metal rods similar to the lightning specialist Ais had killed above.
Another had oversized jaws and thickened tissue around its mouth, evidently designed for absorption.
A third had elongated arms covered in web-like growths disturbingly similar to Arachne's silk.
Lyra stared at that one.
"Oh, I really hate that."
Tsubaki's attention had already moved to another sac, where a flame-shaped glow pulsed behind the developing monster's ribs.
Her expression flattened.
"I hate mine more."
Asfi crouched beside the nearest strand without touching it.
"This is where the specialization happens. The information gathered in previous fights isn't just being passed to new monsters after they hatch. It's changing them before they come out."
Rayleigh looked toward the cocoon with the metal rods.
"So the lightning specialist didn't happen to learn Gonryōmaru."
"No. It was built specifically from what this thing had learned about Ais."
That explained why every new generation had seemed less general and more deliberate.
The longer they fought, the more the source had to work with, and repeated Zanpakutō abilities were no longer merely techniques to imitate.
They were blueprints for counters.
Rayleigh counted more than thirty visible sacs. Several had already begun moving more violently since the team entered.
Ais drew Gonryōmaru.
"We destroy them before they hatch."
"Wait."
Asfi's interruption came quickly enough to stop her.
She pointed toward the three enormous roots anchoring the central body to the surrounding Dungeon.
Their pulse had accelerated.
"Watch the flow. The sacs aren't being fed independently."
Fragments of magic stone moved from the central body into the three roots before returning through smaller branches connected to the developing monsters.
Rayleigh followed the pattern for several seconds.
"The three roots are part of separate circulation routes."
"That's what it looks like."
Lyra glanced between the different sides of the cavern.
"So we cut the big ones and everything drops dead?"
"I didn't say that."
Asfi kept watching the flow.
"I said they're important. That's not the same thing."
Rayleigh drew Ruri'iro Kujaku.
The reaction was immediate. With so many magic stones concentrated in one place, the Zanpakutō's hunger surged through his hand almost eagerly.
'Behave.'
The displeasure he received in return was unmistakable.
Rayleigh ignored it.
"Bloom in a frenzy, Ruri'iro Kujaku."
Lapis-colored vines spread from the blade, but he directed them toward one of the smaller strands rather than the central body.
The growth reacted before they even made contact.
Three sacs split open on the left side of the cavern, spilling unfinished monsters onto the floor in streams of black fluid.
They attacked anyway.
Rayleigh's vines touched the strand.
The amount of energy that rushed into Ruri'iro Kujaku was so violent that his arm jerked.
He severed the connection immediately.
The strand thrashed, and several magic-stone fragments inside the central body dimmed. Before Rayleigh could say anything, power surged back into them from somewhere deeper.
He followed the returning glow.
It had come through one of the three massive roots.
"There."
Asfi saw it too.
"The central body isn't generating all of this itself. Those roots are supplying it."
"Magic stones?"
"Not only magic stones."
She pointed toward the root on the far right. The light moving through it looked different from the concentrated fragments inside the central body.
It was fainter, but spread across a much larger area.
"That one is drawing from the surrounding Dungeon. The smaller veins distribute power and information, but the major roots are feeding the central structure directly."
Ardi looked toward the nearest root.
"Then we cut them."