On August 4, the subsurface exploration Magi Machine known as the "Mole" began its Grand Search of the Inado Mine.
The Mole resembled the shield machines used to bore tunnels on modern Earth—a cylinder measuring two meters in diameter and three meters in length. It was capable of two methods of excavation: magical boring using the magic tool "Dig," and physical drilling using bits tipped with hyper-adamantite.
The excavated soil and debris were discharged to the surface via a transporter. Equipped with Sonar and a magi-detector, the machine scanned for foreign objects as it advanced, ensuring that no valuable buried resources were overlooked. To prevent cave-ins, the magic "Toughening" was applied to the tunnel walls immediately after they were carved.
Because it was conducting a thorough search while digging, the excavation speed was necessarily slow.
It was already known that when the Gigant Peeder had crawled out in the past, there had been unfamiliar magic tools present at the site. However, a cave-in had occurred before their purpose could be confirmed, burying everything deep underground.
"First, our goal is to reach that point two hundred meters down," Laojun directed.
As the Mole churned through the earth, it unearthed small deposits of zinc ore—specifically sphalerite—along the way.
On August 12, at a depth of 50 meters, it found small amounts of arsenopyrite and pyrite.
On August 21, at 100 meters, it mined olivine.
On September 1, at 150 meters, garnet was discovered.
Then, on September 9, it reached the 200-meter mark—the depth from which the Gigant Peeder had first emerged. The Mole proceeded with even greater caution.
"We have found something," reported Smith 3, who was in charge of operating the machine. "It is a broken magic tool. I believe it was crushed by the cave-in."
"Understood," Laojun replied. "Recover it and transport it here."
Following instructions, Smith 3 carefully excavated the device, adjusted the transporter settings, and sent it to the surface.
Then, the digging continued.
On September 10, at a depth of approximately 220 meters, the Mole broke into a hollow space.
"What is this place?"
The cavity appeared to be nearly a kilometer deep and over 300 meters wide. With a height of roughly 20 meters from floor to ceiling, it was a massive cavern. More importantly, it was clearly artificial; the walls, floor, and ceiling were all unnaturally flat.
Smith 3 reported the discovery. Laojun ordered a detailed investigation of the space and dispatched Smiths 4 and 5 as reinforcements. The three small automatons divided the area among themselves and began their survey.
"Mysterious magic tool discovered."
"Mysterious material discovered."
"Mysterious substance discovered."
New discoveries came one after another, leading to an even more shocking find.
"I have located a room that appears to be a processing facility," Smith 3 reported.
By "processing facility," he meant equipment designed for the disposal of biological remains—machinery for incineration or dissolution.
"Given the scale, they must have processed a staggering amount of material."
"What is this...? A golem has been found. However, it is no longer functional."
Ultimately, the haul from the Great Underground Cavern included four mysterious magic tools of the same model, suggesting they shared a common purpose. There were also roughly 50 tons of mysterious biological material, likely harvested from magical beasts. Finally, they found about 20 grams of a mysterious black powder kept in crystal storage containers.
The broken golems yielded nothing of note. While the magic tools were analyzed on-site, the materials and the unknown substance were subjected to rigorous testing by the Smiths. Once they were confirmed to be safe, the items were sent to Hourai Island.
When Jin received the black powder, his eyes widened in shock.
"...Mental catalyst!"
It was the same substance he had received from No. 700672 not long ago.
"Why is this here? No. 700672 said that to harvest this from the creatures of this world, you would need brains on the order of millions."
Just then, a communication arrived from the Smiths.
"Master, Laojun, we have identified the purpose of the magic tools. They function by gathering free ether."
"How is that different from an ether converter?" Jin asked.
"It 'only' collects it. It does nothing else."
"What?"
Essentially, the device gathered free ether from the surrounding space to increase the concentration within a specific area. A short while ago, Jin might have wondered why anyone would want to do that, but now he had a clear idea of the objective.
"Could it be that the demon race... no, the Origins built this?"
The climate was harsh in the north, and free ether was scarce in the south. The solutions were either to adapt to the cold north or to concentrate ether in the south. This equipment was designed for the latter.
"It seems to be far more efficient than the mechanisms used in ether stockers or free ether boxes," Laojun noted.
"I see. I suppose we should call it an 'ether condenser'."
Jin ordered those to be sent back as well. Meanwhile, Laojun reached another significant conclusion.
"My Lord, I suspect this location was a magical beast farm."
Laojun hypothesized that the ancient inhabitants had bred magical beasts in this high-concentration ether environment, then slaughtered them to extract and collect mental catalysts from their brains. Jin had been suspecting the same thing and immediately agreed.
The theory continued that, after many years, the Origins or their descendants vanished, leaving behind only the golems to mindlessly continue their labor. Jin found that plausible as well.
"In any case, I'm grateful to have obtained even a small amount of mental catalyst. Though I might not need it anymore, given the recent treaty."
Still, for a creator, securing rare materials meant expanding the possibilities for the future. It was the stuff of dreams.
"Send samples of that mysterious material as well."
"Understood."
Jin took the material in his hand. It was silver-gray, lustrous, and light. It was flat but irregular in shape, leading to the deduction that it was biological material—likely the carapace of the magical beasts—that had been processed into sheets.
The sheer volume—50 tons—was staggering. He couldn't imagine how many centuries had been spent or how many millions of beasts had been culled to gather that much mental catalyst. It was a cold, industrial scale of slaughter that Jin could never replicate.
However, the best way to honor the remains was for him to put them to good use.
"Hmm... truly an unknown material."
Jin decided to set it aside for now, planning to analyze its specific properties and potential applications later.
"I suspect that the Gigant Peeder was a mutation—perhaps a side effect of the ether condenser's influence," Laojun suggested.
Jin was of the same mind. "There aren't any more of them lurking around, are there?"
"No. Our scans show no such reactions within a one-kilometer radius."
"Good. Leave the cavern investigation to Smiths 4 and 5. Let's have the Mole proceed deeper."
Following his master's order, Smith 3 drove the Mole further into the depths. Since they no longer needed to be quite so cautious, they increased the excavation speed.
Digging 50 meters in a single day, the Mole discovered deposits of native gold, native platinum, and iridosmine. Iridosmine was an alloy of iridium and osmium, a metal so hard and wear-resistant that on Earth, it was used for the tips of high-end fountain pen nibs.
"It doesn't have many immediate uses, but Saki and Toa might get a kick out of it..."
With that thought, Jin stored the samples on his material shelves.
The Mole continued its descent, and at a depth of approximately 500 meters, it struck a substantial vein of magi-crystals. They were milky white in color—standard, all-attribute crystals.
"With a vein this size, the budget for Kaina Village will be secure for the next five hundred years..."
This bounty was made possible only by Jin's advanced technology and the resources of Hourai Island. If one were to calculate the actual cost-benefit ratio, the venture wasn't nearly as profitable as it seemed, but that was a realization Jin would likely never have.