203 — The Regulator Below

The report from the abandoned mines reached Crossroads before Subin's expedition returned from Underpass, and by the following morning, Ara had assembled a working model of the newly discovered structure. She spread the projection across a table in the Crossroads survey office, showing the cavern, its descending platforms, the damaged bridge, and the channels feeding the black-stone installation. The model remained incomplete beneath the central trench, where the sensors had failed to penetrate the dense layers of rock, but it was enough to establish their next objective.

"We know the installation regulates mana flow through the northern mining district," Ara explained. "We also know it was drawing energy faster than the damaged channel could replace it. The Stone Reaver was attracted by that imbalance, and the obstruction turned a manageable situation into a dangerous one."

Jae-hyun leaned over the projection. "So we repair the channel, drive the creature away if it returns, and inspect the lower platform."

"We don't know whether the channel needs repairing or whether it was deliberately configured to operate this way," Ara replied. "If we change the flow without understanding the regulator, we could create a bigger problem than the one we solved."

Subin studied the model. The three intake channels converged beneath the upper structure, while the outlet descended toward the trench. One intake was connected to the old northern mines, another followed the underground river, and the third disappeared into solid rock. The arrangement suggested that the installation gathered mana from several sources before distributing it elsewhere, but the exact destination remained unknown.

"Then our first task is to map the outlet," he said. "We don't need to understand the whole structure today. We need to know what lies below it and whether we can reach it safely."

The Crossroads Wardens approved a second survey under the same agreement established with Varik. Underpass would retain authority over its mining district, while Crossroads supplied technical equipment and experienced surveyors. Subin's team would provide protection, but no one would claim ownership of the installation or the surrounding tunnels.

Two days later, the expedition returned to Underpass with reinforced bridge sections, climbing equipment, portable sensors, and a compact mana-flow analyzer. Varik had arranged additional guards at the northern mine entrance, not because he expected an invasion, but because the recent activity had made it unwise to leave the settlement's access routes unprotected.

The cavern was quieter than before. The Abyssal Stone Reaver had not returned, and the restored channel continued carrying energy through the upper platforms. The damaged bridge had been temporarily reinforced, allowing the engineers to cross in small groups while Subin and the other combat Awakeners watched the trench.

Ara placed sensors along the lower edge of the platform. Their readings revealed that the outlet did not simply descend into the trench; it curved around the central structure and continued through a narrow passage beneath the cavern floor.

"There's a route on the far side," she said. "The rock is too dense for a clear scan, but the channel runs beneath it for at least another two hundred meters."

"Can we follow it from the trench?" Yerin asked.

"Possibly, but the descent is steep, and the walls are unstable. We should use the maintenance ledge first."

A narrow ledge ran around the cavern's eastern wall, partly hidden behind mineral deposits. The engineers secured ropes and anchors while Subin inspected the rock. The path was old but not entirely deteriorated; several sections had been built with the same pale metal used in the regulator's channels. Once the first anchors were fixed, the team began moving along the ledge toward a recessed opening behind the structure.

The passage was barely wide enough for two people to walk side by side. Its walls were lined with shallow grooves, and the floor sloped gradually downward. Unlike the abandoned mine tunnels, it contained no tool marks or collapsed support beams. The route had been built for access to the installation rather than mineral extraction.

After roughly three hundred meters, the passage opened into a smaller chamber containing a row of metal consoles. Most were dark, and several had been crushed by falling stone, but a central panel still emitted a faint blue glow. Ara approached it cautiously, comparing its shape with the instruments found in the upper cavern.

"This looks like a maintenance station," she said. "The regulator may have been monitored from here."

She connected a portable analyzer to the panel. The display flickered, producing a series of symbols that the translator could not interpret, followed by a simplified diagram of the underground channels. The diagram showed the three intakes, the outlet toward the trench, and a second branch that extended farther north before disappearing beyond the panel's damaged display.

"There are two downstream routes," Ara said. "The first is the outlet we found. The second appears to connect to another installation, but I can't determine its distance or condition."

Subin examined the branching diagram. "Can you tell whether the second route is active?"

Ara adjusted the analyzer. The northern branch remained dim, but a faint pulse passed through it every few seconds.

"Partially active. It isn't carrying much energy, though."

Varik, who had accompanied them into the chamber, frowned at the display. "Our oldest mining records mention a northern service road. The miners abandoned it after several tunnels flooded, but no record describes a second regulator."

"Could the road have been closed because the regulator failed?" Yerin asked.

"That's possible," Varik replied. "But we should not assume the two events were connected until we inspect the route."

The maintenance panel showed a control sequence that could redirect some energy from the main outlet into the northern branch. Ara warned that activating it without knowing the branch's condition might increase pressure in a damaged tunnel. Subin agreed that they should leave the controls untouched until they had surveyed the route directly.

The team continued along the maintenance passage, following the northern branch as far as the available supports allowed. The tunnel descended beneath a shelf of black rock and eventually reached a flooded section where the ceiling had collapsed. The water was cold and unusually clear, but mana readings beneath its surface were stronger than those in the surrounding stone.

A narrow current moved toward the collapse.

Ara lowered a sensor into the water. "The channel continues beneath the debris. The water isn't stagnant; it is moving through a submerged passage."

"Can we cross?" Jae-hyun asked.

"Not safely without diving equipment and a better map. The current is pulling toward the collapsed section, and we don't know how deep the passage goes."

Subin crouched beside the water and studied the mineral deposits along the edge. The current had exposed a strip of pale metal embedded in the rock, and its surface bore the same shallow grooves found in the regulator. The submerged passage was almost certainly part of the original system, not a natural cave that happened to intersect it.

A dull impact sounded from beyond the collapse.

The water rippled, and the sensor line jerked hard enough to pull against Ara's hand. She recovered it before the device disappeared beneath the surface.

"Something moved beyond the debris," she said.

Rafael moved in front of the surveyors, while Yerin raised her spear. Subin drew Simple Edge, but he did not approach the water. The impact had come from the far side of the collapsed tunnel, and the pressure readings showed no sudden surge in mana.

A second impact followed, accompanied by a brief disturbance in the current. Something large was moving through the submerged passage, but there was no sign that it was attempting to break through the obstruction.

"Back away from the edge," Subin instructed. "We don't know whether the collapse is the only thing separating us from it."

The team withdrew to a wider section of the tunnel. Ara placed another sensor near the entrance and waited for the readings to settle. The device detected a large moving body beneath the water, then lost its signal as the creature passed beyond the sensor's range.

They had enough information to establish that the northern route remained physically connected to the regulator, but not enough to explore it. Subin refused to let curiosity turn a controlled survey into an underwater rescue operation. They marked the flooded passage, retrieved their equipment, and returned to the maintenance chamber.

Before leaving, Ara managed to recover one additional diagram from the console. It showed the regulator's intended flow pattern, including a narrow bypass that had been shut off. The bypass connected the northern branch to a separate pressure channel, allowing excess energy to move around the main outlet when necessary.

"The bypass may have been closed after the northern passage flooded," Ara said. "If the original channel became obstructed, the regulator would have had fewer options for releasing excess pressure."

"Could reopening it help?" Varik asked.

"It could, but not until we know whether the bypass is intact. If the tunnel has collapsed, forcing energy through it might destabilize the entire system."

Subin studied the diagram once more before turning away from the panel. They now had a practical next step: locate the northern bypass from the opposite side, inspect the flooded passage with proper equipment, and determine whether the regulator could be restored to its intended operating condition.

The expedition returned to Underpass that evening. Varik agreed to send a team to search the old mining records for references to the northern service road, while Ara requested diving equipment and longer-range sensors from Crossroads. The Abyssal Stone Reaver remained somewhere beyond the flooded passage, but there was no reason to pursue it until the team could enter the tunnel safely.

At the settlement's main road, Yerin caught up with Subin as he reviewed the updated map.

"You seem more interested in the regulator than the creature," she said.

"The creature was a problem because the regulator was malfunctioning. If we repair the system properly, we may prevent the same situation from happening again."

"And if the creature comes back before we're ready?"

"Then we'll deal with it." Subin folded the map and returned it to Ara. "But I would rather not fight something powerful just because we failed to prepare."

Yerin smiled faintly. "That almost sounds like sensible advice."

"I give sensible advice quite often. People are simply too distracted to appreciate it."

"Perhaps you should try giving it without sounding pleased with yourself."

They continued toward the settlement's guest quarters, their conversation blending into the noise of workers preparing the northern mines for another survey. The immediate danger had passed, but the work ahead was substantial. A functioning regulator, a flooded service road, and an unexplored underground route now formed a single practical problem, one that could not be solved with swordsmanship alone.

The next expedition would need to reach the submerged bypass from the opposite side. If they could do that, they might restore the regulator without disturbing the creature beneath the water.

For Subin, that was a challenge worth preparing for: not merely defeating whatever stood in his path, but learning enough about the world to choose the right path in the first place.