The corridor narrowed until the walls brushed their shoulders. Heat pressed in small, steady pushes, like a creature testing a door from the other side. Kaen's torch kept its pale composure, but the iron cage around Mira's lantern had begun to sweat. Dren muttered numbers under his breath—sevens and threes—like math could keep the mountain polite.
The passage dropped into a hall shaped like a ribcage. Columns curved overhead and met at a seam of glass, the ceiling frozen mid–wave. In the center stood a black altar fused to the floor. It wasn't pretty stone or priestly. It was practical, the way anvils and cutting boards are practical. Runes circled it in three rings: outer for warning, middle for function, inner for cost.
"Trial site," Kaen said, voice low. "Recently awakened."
"How can you tell?" Dren asked.
"The ash is moved. And the silence is listening."
Yuj stepped to the outer ring. The glyphs didn't flare like before; they brightened just enough to admit he existed. On the altar lay a cracked mask of obsidian, the size of a man's face, with a sliver missing at the left cheek. Around it, veins of green crystal threaded the rock like roots.
Mira lifted her lantern. "That's not flame ore."
"Life trace," Yuj said. The green lines pulsed once, faint and patient. He felt the answering flicker under his own skin, the thin memory of a leaf that had no business growing in a furnace. He kept his hands at his sides.
Letters formed above the mask, strokes of light writing themselves into being. The script wasn't Academy standard; it was older, the kind that assumed you'd feel meaning even if you couldn't pronounce it.
"Second trial," Dren said, translating faster than he had a right to. "The Heart of the Mountain. Bind or be bound. Fuel must say its own name."
"Say your fuel," Kaen repeated. "Or the mountain names it for you."
Alaric's warning returned: find your fuel before it finds you. Yuj licked his lips. "We do it together," he said. "In order. A little, not too much."
Dren nodded immediately, relief grabbing his voice. "I'll go first. I don't… burn much." He stepped to the inner ring and pressed his fingertips to the altar. "My fuel is fear," he said, too quickly, as if speed could blunt the edge.
The mask breathed. The hall darkened. A shade rose from the altar with Dren's eyes and Dren's hands but none of his softness. It leaned over him, inhaled the fear like steam, and faded. A score scratched itself into the stone: a single short line.
"That's it?" Dren laughed, then flinched at his own sound. "That's fine. Fine is good."
Mira went next. "Mine is hope," she whispered, jaw set so the word wouldn't tremble. The shade that rose wore a face he didn't recognize—a child with lantern-light hair standing alone at a gate—and then it was gone. Two lines on the stone.
Kaen didn't wait for a cue. He placed one palm flat. "Order."
The mask cracked wider, as if smiling in a language that had no joy in it. The shade that lifted wore Kaen's posture and none of his mercy. It measured, catalogued, avoided error. The air around it cooled until Yuj saw his breath. It bowed to Kaen, precise as a blade returning to its sheath, and sank back into rock. Three lines scored the altar. The inner ring brightened.
Yuj swallowed. He could lie. He could say purpose, responsibility, strength—any word a school would approve. The green trace under his skin pulsed again, not insisting, only reminding. He set his hand down.
"My fuel," Yuj said, "is regret."
The hall answered like a lung at the bottom of a scream. The shade that rose wore too many faces. It became Yun for a heartbeat, soot on her cheek and ribbon at her ear. It became the baker's son dragging buckets against a red sky. It became a boy he had never met, burning himself brave while no one watched. Then it was only heat, raw and hungry, the old appetite trying to take the room.
"Stop," Kaen said sharply.
Yuj didn't move his hand. He spoke to the flame like Alaric had told them to speak to themselves. "Eat less," he said. "I'll give you purpose after."
The shade tilted its head, curious as a dog that hadn't decided whether to bite. The green vein in the altar brightened, a counterweight Yuj hadn't asked for. The red drew back a degree, tamed by the idea of a future.
Four lines scored the stone. The rings burned in sequence—outer, middle, inner—then collapsed inward like doors locking. The mask split completely. Behind it, not a cavity but a heart: a knot of crystal and coal beating once every few breaths. With each pulse, heat rolled through the hall. Between pulses, the air listened again.
"Bind or be bound," Dren repeated. "What did we just bind?"
"That," Kaen said, nodding at the heart. "Or it bound us."
A fracture ran along the left wall, thin as a cut. Light seeped through it in two colors that did not belong together: red as the inside of a forged blade, green as a leaf lit from the back. Yuj's throat closed for a step and then opened again.
"Through there," he said.
The crack became a doorway when Kaen touched the seam with his cool fire. Stone sighed and parted. A smaller chamber waited beyond, shaped like a bell. Its floor was a circle of glass laid over a well of light. At the bottom of the well something moved, slow as the thought of a dream. Petals? Embers? Both?
Mira knelt, lantern casting careful gold. "There are words around the rim."
"Read," Kaen said.
Dren swallowed and leaned in. "When the mountain's heart remembers, the world will be asked to forgive."
Yuj stared into the well until the world around the circle went soft. The light at the bottom brightened, then blurred, then took the shape of a girl's hand pressed to the underside of the glass. It was impossible, a trick, a wish. He put his own palm down, not touching, hovering a finger's width above.
"Yun?" The name left him before he remembered he wasn't supposed to say it.
Nothing rose to meet it. Only light. Only heat.
The glass jumped under his hand. Not much. Just enough to say I heard. Then the light went dull again, and the well looked like glass over old coals.
Kaen had not moved. His voice came from the doorway, even and thin. "We log two facts. One: the heart is active. Two: it responds to certain fuels."
"What does that mean in a language that helps us not die?" Mira asked.
"It means," Yuj said, surprising himself by sounding calm, "we don't feed it by accident."
The corridor ahead took a left as if the mountain had changed its mind halfway through being built. The new passage was cooler. The walls weren't red glass but darker stone banded with iron. Yuj felt the inner itch that came before a place told you its rules.
Alaric's voice walked the hall before any of them did. Not in person. Etched into the wall, ten words at shoulder height, carved by hand long ago.
Do not mistake pain for fuel. Do not mistake fuel for law.
"Teacher handwriting," Dren said faintly. "That's his."
Kaen brushed the letters with two fingers. "He's run this path more than once."
The tunnel ended in a door that had never decided to be a door, just a round cut in the stone with no hinge and no handle. The trial rings circled it—outer warning, middle function, inner cost. In the center, a shallow depression waited for a hand. Yuj didn't like how neatly it matched his own.
"Don't," Kaen said, as Yuj lifted his palm. "We test another way first."
Kaen drew the knife he had used before and pricked his thumb. A bead of blood welled, blue-white frost smoking from the cut. The air went colder, the torch shrank to a strict flame. He let a drop touch the depression.
The mountain shivered. The door did not open. Far below, something groaned like deep rock rolling over. The depression rimed with thin ice, then cracked and thawed in the same breath.
"What did we learn?" Yuj asked.
"That certain fuels offend it," Kaen said, wrapping his thumb. "Or it has a sense of humor."
Yuj stared at the waiting circle. He thought of Alaric's ten words, of the altar, of the shade wearing too many faces. He thought of the heart pulsing beneath the floor and the green line under his skin that had not asked to be a secret but was trying to be kind about it.
"I'll try," he said.
"Don't bleed," Kaen said, the warning softer this time.
Yuj set his hand to the stone. He didn't push flame. He didn't call power. He exhaled the way Alaric had taught: count five in, five out, and say your name inside so the fire remembers you're a person. Under his palm, heat rose and then balanced. A green whisper twined through it like a thread through cloth.
The door opened with the sigh of an old room letting out a secret.
Beyond it lay stairs falling into red dark, a heat that spoke in low language. The breath that came up smelled like iron, rain, and something sweet from a memory he was not ready to own.
Dren licked his lips. "This is where we should turn back and make a very good report."
"Or make a better one," Mira said, sheathing her fear like a blade.
Kaen's eyes met Yuj's across the threshold. "Cataloguing variables," he said, as if to himself. "One: you. Two: me. Three and four: unknown. Five: teacher intent."
"Six," Yuj said. "Whatever is waking."
He tightened the ribbon. The knot sat above the little green light in his skin. He didn't look down into the stair-well long enough to think of falling. He took the first step.
The heat rose like applause.
Behind them, very softly, Alaric's ten words on the wall warmed until they glowed. Ahead of them, the mountain's heart kept time.
They went down toward it, and the dark smiled like something that had been waiting for their names.