In the afternoon.
Sunlight hit the copper floor around the hole, reflecting a somewhat piercing glare.
Bolen crouched about forty meters from the opening, his right hand pressed against the surface of a copper plate while his left leaned on his cane.
Kail crouched beside him, holding a small notebook and a charcoal pencil to record everything at a moment's notice.
Lu Yuan had brought two Nightwatchers to stand guard on the perimeter.
The direction of the hole was very quiet.
It was always like this during the day.
Bolen's hand moved slowly across the copper surface.
He stopped at regular intervals, tapping his fingers a few times and tilting his head to listen to the sound echoing within the copper plate.
"Pry this one open."
Kail took a flat chisel from the toolbox and pried along the edge of the copper plate a few times.
The copper plate loosened, revealing a layer of compacted soil beneath and a copper pipe embedded in the dirt, slightly thicker than a finger, with fine patterns engraved on its surface.
Bolen leaned down to look.
He watched for about half a minute.
Then he straightened his back and scanned the surroundings.
"Pry open two more. That one on the left, and the third one in front."
Kail did as instructed.
After the three copper plates were lifted, three sections of conduction pathways were exposed on the ground.
Lu Yuan noticed Bolen's expression change.
The old man was usually in a state of excitement whenever he saw inscriptions, his eyes bright and his fingers constantly tracing patterns.
But now, he crouched by the second copper plate, motionless.
"What is it?" Lu Yuan walked over.
Bolen did not answer immediately.
He pointed his finger at the soil layer revealed after the copper plate was lifted.
"Look at this."
Lu Yuan crouched down.
The soil had been disturbed.
It wasn't natural settling or hardening; there were traces of it being dug up and then backfilled.
The texture of the backfill was looser than the surrounding earth, and the color was slightly different, with the freshly turned soil being a shade darker.
"When was this from?"
Bolen picked up a small clump of soil and rubbed it between his fingertips.
"Hard to say. But it wasn't long ago," he flicked the soil fragments away.
"This level of looseness... a few months? Half a year? It definitely wasn't left from when it was originally laid down."
"Can you see anything else?"
"No." Bolen stood up and walked to the other two opened copper plates.
He checked them one by one.
Two of the three spots had similar traces of disturbed soil.
Bolen's brow furrowed tighter and tighter.
"Someone lifted these copper plates not long ago, moved the conduction pathways underneath, and then covered them back up."
He glanced at Lu Yuan.
"It wasn't a repair; a repair would leave marks of welding and polishing, which aren't here. It's more like... an inspection."
Lu Yuan didn't speak.
Greyish-white text flickered quietly at the edge of his vision.
【Bronze City Status: +1...4/50】
Bolen didn't care what Lu Yuan was thinking. He was already flat on the ground, his face almost pressed against the surface of the copper pipe of the conduction pathway.
"Light," he reached out toward Kail.
Kail handed over a small copper hand-lamp filled with alchemical phosphorescent liquid.
A pale blue light shone on the copper pipe, making the patterns on the surface very clear.
Bolen watched for a long time.
Then he took out a small knife and lightly scraped a cross-section of the copper pipe where it had already broken.
What he scraped off was not copper shavings.
It was a layer of dark powder.
Lu Yuan leaned in to look.
The cross-section of the copper pipe showed two layers of color.
The outer layer was normal copper color, slightly darkened by oxidation.
But on the inner wall of the pipe, there was a ring of dark brown corrosion marks, as if something had burned it from the inside.
"We have trouble." Bolen's voice dropped low.
"The corrosion direction is reversed."
"What do you mean?"
"Normal metal corrosion goes from the outside in; the outer layer contacts the substances in the air and soil first, so it fails first." Bolen pointed his knife at the pipe's cross-section.
"But for this pipe, the corrosion on the inner wall is far more severe than the outer wall. In some places, it's eaten right through, while the outer wall remains intact."
Bolen straightened up and walked to the second and third sections of the pathways, checking them one by one.
All three sections showed severe decay on the inner walls.
Lu Yuan looked at those cross-sections.
The conduction pathways were the pipes that transported the power of the city wall runes from the inner city to various parts of the outer city.
Power flowed through the inside of the pipes.
If the pipes were decaying from the inside first...
"There's a problem at the source," Lu Yuan said.
Bolen nodded.
"The thing flowing through them is no longer clean."
His tone shifted from excitement to solemnity.
"The city wall runes are still lit, though they grow dimmer by the day, which means power is still being output. But right now, the output power is corroding its own pipes." Bolen paused for a moment.
"Copper, silver, and gold are known as the three great banes of the eerie. Something that can flow within copper and even reverse-corrode copper structures... I've been doing this for decades and have never seen such a thing."
Lu Yuan didn't respond.
He thought of those bronze pillars he had seen at the bottom of the abyss.
Bolen had also been down the hole, touched the bronze pillars himself, and knew those massive bronze structures jutted out from the cliff walls, angling into the abyss.
But Bolen didn't know that the bronze pillars pointed toward the inner city.
Even less did he know what that implied.
Lu Yuan didn't believe the Nightwatchers were unaware, so he didn't intend to tell anyone else for the time being.
Especially this old fellow Bolen.
Lu Yuan had a premonition that if he spoke, this old man would immediately find an excuse to run away.
"I can fix this pipe," Bolen tapped the copper pipe.
"Treating the cross-sections and applying purification to the decay is no problem technically."
"But if the power of the bronze truly is contaminated, it won't last long even after I fix it."
"Do we still repair it?"
Bolen leaned on his cane and stood up, his knees giving a sharp crack.
"Repair it."
Lu Yuan looked toward the hole.
"Tell me what you need."
Bolen nodded and crouched back down.
Bolen moved his entire toolbox next to the first break.
Kail opened the box, and the items inside were more numerous than Lu Yuan had expected.
Copper-bristle brushes and needle-like objects of various calibers.
A row of sealed copper tubes, several bottles of dark liquid, and a full set of engraving knives.
From the thickest to those as fine as a needle tip, over a dozen were tucked into a leather roll.
Bolen crouched before the break, first using the copper-bristle brush to clean about a palm's width on both sides of the cross-section.
Then he closed his eyes.
He placed both hands flat on the severed surfaces of the copper pipe.
After a moment, a faint blue-white shimmer began to glow from Bolen's fingertips.
The shimmer spread from his fingertips to his palms and then seeped into the copper pipe surface where his fingers were pressed.
The areas on the inner wall of the copper pipe covered in dark brown corrosion began to react.
Dense patterns emerged on the inner wall.
Bolen's fingers hovered over those patterns.
He didn't touch them.
Blue light flickered in his pupils.
It pulsed at the same frequency as the shimmer on his fingertips.
"Kail, record this," Bolen's demeanor changed; he was no longer the mumbling old man from before.
"First cross-section, inner wall inscription residue clarity is about sixty percent. The model is consistent with the city wall terminals on the surface, but the engraving depth is increased by two to three times. The base patterns still exist and can serve as anchors."
Kail's pen moved rapidly.
Bolen pulled a medium-sized engraving knife from the leather roll.
The tip of the blade hovered less than a millimeter above the inner wall of the copper pipe.
He didn't strike immediately.
Instead, he used his left index finger to tap a spot on the inner wall that Lu Yuan couldn't see anything special about.
The blue-white shimmer at his fingertip lingered on that spot for an instant.
A tiny vibration came from deep within the copper pipe wall.
It was as if something had been awakened.
With that point as the center, a ring of patterns that Lu Yuan completely failed to understand surfaced from within the copper wall.
The lines were thinner than a hair, intersecting and winding, appearing as a dark gold color under the blue-white shimmer.
Bolen stared at those patterns for about five seconds.
Then the engraving knife fell.
It precisely cut into the break of one of the patterns.
The sound of the blade tip sliding across the copper wall was almost inaudible.
But after every stroke, those dark gold patterns brightened a bit more.
Bolen's breathing became rapid, as if he were consuming a massive amount of physical energy.
Yet the speed of the engraving knife in his hand was extremely fast.
However, there was a very brief pause between each stroke.
In that moment of pause, he would re-perceive the flow of the patterns before making the next cut.
Lu Yuan stood nearby, watching motionlessly.
He couldn't understand those patterns.
The greyish-white text didn't provide any further analysis either.
But he could see what Bolen was doing.
He was reconnecting that invisible inscription network within the inner wall of the copper pipe, one line at a time.
Every time a line was connected, the surface of the copper pipe would heat up slightly.
The shimmer spread from the break to both sides.
One break.
Bolen spent nearly forty minutes on it.
When he finished, he straightened his back, tucked the engraving knife back into the roll, and the blue-white shimmer on his fingers slowly faded.
The blue in his pupils also dimmed.
The old man's face was covered in sweat.
And at the same time, the greyish-white text flickered at the edge of his vision.
【You have observed the repair and diagnosis process of an inscription conduction structure......】
【New knowledge unlocked.】
【Inscription (Basic): +0.1...0.1/10】
Lu Yuan's brow quirked at the sight; it actually worked.
"Next one," Bolen said to Kail.
Kail had already moved the toolbox to the side of the second break.
Throughout the afternoon, Bolen repeated this process three times.
Three breaks.
A total of about forty meters of conduction pathways were reconnected.
By the time the third one was finished, Bolen's hands were trembling slightly.
【Inscription (Basic): +0.1...+0.1...0.6/10】
"It's done." He patted the dirt off his knees. "The piping here isn't a single unit with the runes on the city wall; the technique in several places is clearly flawed."
"But thanks to that, otherwise I wouldn't have been able to finish today. We'll see the results after dark."
"When the city wall runes light up, power will automatically be transmitted," Kail added.
"If it's connected, the surface of the copper plates in this section should show a faint glow."
"Assuming the city wall runes can still light up tonight," Bolen muttered.
The sun had not yet set.
Lu Yuan brought Bolen back to the Alchemy Workshop.
Glock was on the first floor.
"Did you find anything?" Glock looked at Bolen's state with some confusion.
Bolen leaned against the wall, not speaking.
Lu Yuan spoke for him.
"Two things."
"First, someone lifted the copper plates in the North Ward area not long ago, moved the conduction pathways underneath, and then covered them back up. It happened roughly within the last few months to half a year."
Glock's eyes narrowed slightly.
"I will investigate that."
"Second."
"The copper pipes of the conduction pathways have more severe corrosion on the inner walls than the outer walls."
Glock was not an inscriptionist, but he understood the keyword.
"Rotting from the inside?"
"Yes," Lu Yuan said.
"The substance flowing through them has a problem, but I don't know exactly what it is."
Glock looked at Bolen.
"Are you sure?"
Bolen remained silent for a moment before finally nodding.
"Copper pipes corroding from the inside... I've never seen it in decades. There's only one explanation: the power being transmitted itself carries corrosiveness."
Glock leaned his hands on the map table and looked down for a while.
"This situation must be reported to the branch." He looked up.
"Damn it, since when did so many things start happening in the Bronze City!"
Glock thought for a moment, then asked.
"Bolen." He called out. "In the section you repaired, can you judge the trend of the contamination?"
"I can." Bolen's voice was a bit hoarse.
"The speed and depth of the pipe wall corrosion will change in sync with the level of contamination at the source. I just need to check it every few hours."
"Good." Glock straightened up.
"I'll head into the city directly in a bit. None of you are to speak a word to anyone outside about someone moving the copper plates."
He glanced at Lu Yuan and Bolen respectively.
"I'll handle the explanation to the branch, but until we figure this out, this matter doesn't leave the Alchemy Workshop."
Neither Lu Yuan nor Bolen had any objections.
Glock turned and went upstairs to write his report.
Night fell.
The fifth night.
The city wall runes lit up.
They were another layer dimmer than last night.
Lu Yuan stood at the front of the new position, with the compressed defensive line behind him.
Toward the hole, it was pitch black.
At the edge of his vision, the greyish-white text remained quiet.
【Environmental Perception: Minimal pollution sources detected...】
The fifth night.
The ghouls still hadn't come.
Lu Yuan did not relax.
He was waiting for the reaction of that section of conduction pathways.
In the rear, Bolen hadn't returned to the Alchemy Workshop either.
The old man was wrapped in an old coat, crouching by the section of copper plates he had repaired in the afternoon, both hands pressed against the ground.
Kail crouched beside him, the hand-lamp placed at his feet.
And then—
"Lu Yuan!"
Bolen's voice came from behind.
It wasn't loud, but it was urgent.
Lu Yuan signaled Bo Er to keep an eye on the front and walked over quickly.
Bolen's hands were still pressed against the copper plate.
His face looked very pale under the pale blue light of the hand-lamp.
"Look."
Lu Yuan looked down.
Patterns had appeared on the surface of the copper plate.
The conduction pathway Bolen repaired in the afternoon was indeed connected.
A faint light from the inscription patterns began to manifest on the copper plate surface.
But the color was wrong.
Normal rune conduction light should be a ghostly blue.
The light surfacing on this section of copper plate carried a layer of grey-green.
The grey-green light slowly spread along the inscription patterns, flowing from the direction of the hole toward the position.
"The direction is wrong." Bolen's voice was tight.
"The transmission direction of the city wall runes is from the inner city to the outer city. But this light is moving up from the direction of the hole."
"It's coming from underground."
Bolen nodded.
"The pathways are bidirectional. Something on the other end is back-flowing."
At the edge of his vision, the greyish-white text jumped out.
【Environmental Perception: Unknown pollution source detected... Distance is advised...】
"Can you cut this connection?" Lu Yuan asked immediately.
"If we don't, the underground contamination will seep to the surface through the pipes," Bolen said quickly.
"If this thing can contaminate bronze with inscriptions, it can certainly contaminate the ground without them."
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