The morning air carried an unusual warmth despite the mountain altitude, and Misaki noticed it immediately as he and Thel'mor walked toward the bridge site. His engineer's instincts catalogued the anomaly: temperature approximately fifteen degrees warmer than expected for this elevation, humidity levels suggesting active heat source, and a persistent low hum that resonated through the stone beneath their feet.
Then he saw the chimneys.
Massive stone structures rose from the valley floor like artificial mountains, each one releasing thick columns of steam that caught the morning light and transformed into luminous clouds. The vapor didn't dissipate quickly—it hung in the air with unusual density, creating a permanent fog bank that drifted across the lower city districts.
"What is that?" Misaki asked, stopping mid-stride to stare.
Thel'mor followed his gaze with the casual familiarity of someone who'd seen the sight his entire life. "The central refineries. They process raw mythril ore from the quarries and also serve as the city's heating source." He gestured toward the buildings surrounding them. "Everything you see in the lower districts is kept warm year-round through the vapor distribution network."
Misaki's mind immediately began working through the implications. District heating on this scale required sophisticated engineering—pressure regulation, temperature control, distribution infrastructure, maintenance protocols. "Can we go see it? The refinery system?"
The apprentice blinked in surprise. "It's not really relevant to bridge construction..."
"Everything is relevant to bridge construction," Misaki countered. "We're building a crossing that will face extreme winter conditions. Understanding how Seleun'mhir manages heat distribution could inform our design." He was already walking toward the nearest chimney. "Besides, I'm an engineer. I need to see how things work."
Thel'mor hurried to catch up, his sixty years of life experience reminding him that Senior Engineer Kalth'ren had specifically said this otherworlder "thought differently." Perhaps indulging his curiosity would prove valuable.
The Central Mythril Refinery occupied a carved-out section of the mountain's base, its entrance marked by massive bronze doors that radiated heat like living things. Inside, the temperature jumped immediately—not uncomfortably hot, but noticeably warmer than the external mountain air.
A refinery supervisor named Calvek met them in the main observation gallery, a balcony overlooking the processing floor where workers moved with practiced efficiency among machinery that hummed with barely contained energy. Calvek was perhaps three hundred years old, his grey hair pulled back in a practical braid, his hands bearing the permanent calluses of someone who'd spent centuries working with metal and heat.
"State your business," Calvek said, his tone professional but not unfriendly.
"Educational tour," Misaki replied. "I'm Misaki Haruto, assigned to the Kresh'val bridge reconstruction. I saw your chimneys and wanted to understand how the heating distribution system works."
Calvek's weathered face showed genuine interest. "The bridge engineer wants to study refinery operations? That's unusual."
"I believe in understanding all systems that might influence my designs. Winter ice accumulation destroyed the last bridge. I want to know if there are heat-based solutions we haven't considered."
The supervisor's expression shifted to respect. "A man who asks the right questions. Come. I'll show you how we keep this mountain city habitable."
He led them down to the processing floor, where the true scale of the operation became apparent. Massive furnaces lined the walls—each one built from fire-resistant stone quarried from the deepest mountain chambers, each one burning with flames that glowed blue-white rather than the normal orange-red of conventional fires.
"Mythril ore," Calvek explained, gesturing to the furnaces, "requires extreme temperatures to process. We're talking about fifteen hundred degrees at minimum. Most metals would simply melt and pool. But mythril undergoes a unique transformation when heated beyond its melting point—it vaporizes."
Misaki's engineering background immediately flagged this as extraordinary. "Metals don't normally vaporize at accessible temperatures. That would require—"
"Temperatures that would be impossible with conventional fuel, yes," Calvek agreed. "But we're not using conventional fuel. The furnaces burn concentrated Tra'ji fire wood supplemented with powdered mythril catalyst. The mythril in the catalyst actually feeds the reaction, creating a self-sustaining thermal loop that reaches the necessary temperatures."
They approached one of the furnaces where workers were loading raw ore through reinforced hatches. The heat was intense even from ten meters away, making the air shimmer and dance.
"Once the mythril vaporizes," Calvek continued, "it enters the collection system." He pointed upward to a network of massive pipes—each one as thick as a man's torso—that extended from the furnace tops toward the ceiling. "The vapor is extremely hot—around eight hundred degrees—and it has unusual thermal retention properties. Normal steam would cool rapidly and condense. Mythril vapor maintains its heat for hours."
Thel'mor was taking notes frantically in his journal, his young mind clearly struggling to absorb the technical complexity. Misaki, however, was following perfectly, his aerospace engineering background providing the theoretical framework to understand the thermodynamics at play.
"The pipes distribute the vapor throughout the city?" Misaki asked.
"Exactly. But not as vapor directly—that would be too dangerous. Temperatures that high would cook anyone who came near the distribution points." Calvek led them to a secondary chamber where the pipes split into progressively smaller branches. "The primary collection pipes feed into heat exchange chambers built into every major building and street in the lower districts."
He showed them a cutaway diagram mounted on the chamber wall—a cross-section of a typical building showing the internal heating infrastructure. Hollow columns ran through the walls at regular intervals, and similar channels were embedded in the floor systems. The diagram showed hot mythril vapor flowing through sealed primary pipes that ran adjacent to these columns but never directly into them.
"Heat exchange," Misaki said, understanding immediately. "The vapor pipes transfer thermal energy to the building's internal column network without direct vapor contact."
"Precisely. The primary pipes reach temperatures of seven to eight hundred degrees. That heat radiates into the building columns, which are filled with air. The air heats to maybe fifty to sixty degrees—warm enough to heat the interior spaces comfortably, but not dangerously hot." Calvek pointed to vents in the diagram. "The heated air rises naturally through the columns, creating a convection current that circulates warmth throughout the building. Cold air is drawn in at the base, heated as it rises, released at the top, and the cycle continues."
"Passive circulation," Misaki observed. "No mechanical pumps required. The heat differential creates the airflow naturally."
"Exactly. The system has been running for over two thousand years with minimal maintenance because there are no moving parts to break down. We just need to ensure the primary vapor pipes remain sealed and the furnaces stay operational."
Thel'mor looked up from his notes, his expression thoughtful. "But how does this help with the bridge? We can't exactly run mythril vapor pipes across a two-hundred-sixty-meter span."
Misaki was already sketching in his own notebook, his hand moving rapidly as ideas coalesced. "Not vapor pipes, no. But the principle of embedded heating channels..." He paused, calculations running through his mind. "What's the minimum temperature differential needed to prevent ice formation?"
Calvek considered. "On stone or wood surfaces? You'd want to maintain the surface temperature above freezing—so at least five to ten degrees above zero. That prevents ice accumulation even during heavy snowfall."
"And how much heat would that require for a bridge surface approximately two hundred sixty meters long and..." Misaki checked his survey notes, "three meters wide?"
The supervisor pulled out an abacus from his work desk and began calculating with practiced efficiency. His fingers moved across the beads with the speed of someone who'd performed similar calculations for three centuries. "Assuming average winter temperatures of minus fifteen degrees, accounting for wind chill from mountain passes, factoring in the thermal mass of the bridge materials... you'd need approximately two thousand kilojoules per hour to maintain that surface temperature differential."
Misaki converted the units in his head. "That's about half a megawatt of continuous heating. Achievable, but it would require a dedicated heat source."
"Which brings us back to the problem," Thel'mor interjected. "We can't run vapor pipes from the refinery to the bridge site. It's twelve kilometers away, and the terrain includes vertical elevation changes that would make pipe routing impossible."
"No," Misaki agreed, still sketching. "But what if we don't need to?"
He turned his notebook to show them what he'd drawn—a bridge design that looked radically different from the standard suspension bridge Kalth'ren had initially proposed. This design was narrower, sleeker, with a walking surface that appeared almost skeletal in its minimalism.
"The original bridge design called for a three-meter-wide deck with full planking," Misaki explained. "Maximum weight capacity, maximum surface area. But maximum surface area also means maximum heat loss. Look at this alternative."
His sketch showed a bridge only one and a half meters wide—narrow enough that two people could pass each other but not wide enough for wagons or carts. The deck wasn't solid planking but rather a grated metal surface with air gaps between the walkway slats.
"Why the gaps?" Calvek asked, leaning in to study the design.
"Two reasons. First, reduced weight means less structural stress on the mythril cables and anchor points. Second—and this is critical—the gaps allow wind to pass through rather than creating resistance. The old bridge failed partly because accumulated ice added massive weight to a surface that also caught wind like a sail. This design eliminates both problems."
Thel'mor was nodding slowly, his engineering training helping him see the logic. "Less surface area to heat, better wind dynamics... but you still haven't solved the heat source problem."
Misaki flipped to a new page and began sketching a detailed cross-section of the bridge deck. "What if we embedded heat-retention materials directly into the walking surface? Not active heating, but passive thermal mass that absorbs heat during the day cycle when Ulth'rk is high, and releases it slowly during the night cycle?"
"That wouldn't be enough for winter," Calvek said immediately. "Ulth'rk's heat during winter months is minimal. You'd get maybe a two-degree differential at best."
"True. But what if we supplemented it?" Misaki's pencil was moving faster now, details emerging on the page. "Small mythril heating elements embedded at regular intervals along the deck. Not continuously active—that would require too much energy—but activated periodically when temperature sensors detect ice formation risk."
He showed them a design where thin mythril rods were embedded into the bridge decking at one-meter intervals. Each rod could be heated using small Tra'ji fire wood chambers built into the bridge's anchor points at both ends.
"You'd heat the rods at the anchor stations," Misaki explained, "where we can build proper furnaces into the mountain rock face. The mythril's thermal retention properties would carry that heat along the entire length of the rod for hours. When the rod temperature drops below a threshold, you reheat. Cycle repeats."
Calvek studied the design with the critical eye of someone who'd spent three centuries evaluating engineering proposals. "The mythril rods would need to be at least two centimeters thick to carry sufficient thermal mass. That's expensive."
"Less expensive than rebuilding the bridge every four hundred years," Misaki countered. "And consider the economic value—a bridge that remains passable year-round instead of closing for three months every winter. The trade revenue alone would justify the construction cost within a century."
Thel'mor was practically vibrating with excitement. "This is brilliant. We could reduce the bridge width, cut the total weight by sixty percent, improve wind resistance, and add functional winter heating. Senior Engineer Kalth'ren needs to see this immediately."
"One more thing," Misaki added, sketching final details. "The narrower design actually creates a better pedestrian experience. Three meters feels industrial, utilitarian. One and a half meters with open sides creates an intimate crossing—you feel connected to the landscape rather than isolated from it. Psychology matters in infrastructure design."
Calvek nodded slowly, genuine respect evident in his expression. "You think like someone who plans to be here long enough to see their work age. Most young engineers focus on immediate functionality. You're considering century-scale implications."
"I learned that here," Misaki said quietly. "In a world where people live eight hundred years, infrastructure isn't temporary. It's legacy."
They returned to the Engineering Corps workshop carrying rolled diagrams and detailed calculations. Kalth'ren took one look at Misaki's revised design and immediately called for a full technical review with the mountain engineering council.
The heated bridge concept—narrow, wind-resistant, with embedded thermal regulation—would revolutionize mountain crossing infrastructure throughout Seleun'mhir.
All because a refugee engineer had noticed some chimneys and asked questions.