The apprentice library smelled of wet plaster and old paper. Yan had spent the morning helping Gu replace the split face of the practice slab. The new board was pale and clean, its edges fitted into the frame without the metal lip that had caught Yan’s hand. A fresh strip of cloth covered his knuckles. The cut had closed, but the skin tugged when he bent his fingers.
Gu tested the frame with the heel of his hand. It held without a rattle. Then he tapped the new face twice with a wooden mallet. The sound was solid, though a little hollow near the lower brace.
“Does that mean it’s ready?” Yan asked.
“It means it is ready for one careful strike.” Gu put the mallet away. “It is not ready for you to decide the whole library has become a target.”
“I only wanted to know whether you had replaced the face or the frame.”
“And now you know.” Gu wiped his hands on a rag. “Come inside.”
He led Yan past the front shelves to the cabinet room. The key ring on his belt held a dozen keys, all marked with narrow strips of wood. Gu picked out a small iron key and opened a second cabinet, one set behind the first. Its shelves held damaged manuals, partial copies, and books with pages missing from their bindings. Each had a tag noting what could be read and what remained uncertain.
Yan looked at the row of labels. “These are the damaged texts?”
“Some. Some are incomplete. Some have bad copying. A few have warnings that were separated from the instructions.” Gu pointed to the shelf nearest the door. “You may use these under supervision. That does not mean you may practice everything you can read.”
“I understand.”
“Do you?” Gu placed the key in Yan’s palm. “Before you activate any new method, your record needs its source, complete instructions, expected benefit, and intrinsic cost. If one of those is missing, you record the gap and wait.”
Yan turned the small key between his fingers. It left a dark mark on his thumb. “That will keep my notes from pretending I know more than I do.”
“It may also keep your bones where they belong.”
“I didn’t say it would make the method safe.”
Gu watched him for a moment, then nodded. “Good. You’re responsible for the key. It stays with you only while you are working here. At closing, it comes back to me.”
Yan tucked it into the inside pocket of his coat, separate from the folded sequence he had copied. “What happens if a text has all four things and is still dangerous?”
“You learn what the warning says. You ask me to check it. If the danger remains beyond what we can control, you do not practice it.”
“And if it has a cost that I can bear?”
“Then we consider what evidence you have, what the room can withstand, and who else might be affected.” Gu gestured toward the practice alcove. “Having a complete page is not the same as having permission to be foolish.”
Yan gave him a sideways look. “You could put that on the cabinet.”
“I’d have to write it every morning for you.”
At the desk, Yan opened the Ashen Marrow Scripture’s case. He checked that the red warning tag still sat beside the corrected sequence. The release point and stop condition were written on the same page as the measured breaths. He returned the scripture to its place, keeping the warning attached to the sequence copy in his notebook.
Gu watched him close the case. “Tell me how this differs from the cough tonic you brought in last month.”
“The tonic was made to soothe Ning’s throat. It acts on an ordinary symptom, and it doesn’t send qi through a route or ask the bones to take pressure.”
“And the Ashen Marrow method?”
“It deliberately circulates qi through the marrow. For an ordinary cultivator, the third full circuit can destroy it. The internal strain changes for me. That doesn’t change what a strike can do to a target or to my skin.”
Gu tapped the wrapped knuckles lightly with one finger. Yan flinched, then breathed out. The skin pulled beneath the cloth.
“That still hurts?”
“When it brushes an edge or bends too far.”
“Then we keep it wrapped. One strike, and you stop if the bandage shifts.”
Yan went to the alcove. The repaired practice face stood against the brace. The old strike line had been replaced with a narrower mark set in from every edge. Yan checked the frame and placed his feet on the chalk guides. He gathered a small charge, followed the learned sequence, and released it at the center of the board.
The wood cracked along the mark. The sound traveled through the frame, but the braces held. Yan drew his fist back. His marrow felt warm and settled, the familiar strengthening result. His wrapped knuckles brushed the rough edge of the board as he lowered his hand. The cut tugged sharply.
He stopped and looked at the cloth. A faint reddish spot appeared at the fold, but it did not spread.
Gu put the mallet aside. “That’s enough.”
“I can do another—”
“You can. You won’t.” Gu lifted the split face out of the frame and inspected the fracture. “The board did what we asked. Your hand did not need another contact.”
Yan flexed only the uninjured fingers. “The marrow is fine.”
“I know. The skin is still closing.” Gu laid the board on the bench. “The replacement costs two strings of copper from my book allowance.”
“I broke it. I should pay half.”
“You did not break the frame.”
“The practice face was new.”
“It was made to be struck.”
“And now it needs another one.” Yan reached for his coin pouch, but Gu placed a palm over it.
“My allowance can cover a practice face. You are saving for Ning’s treatment.”
“I can contribute without emptying the pouch.”
Gu considered him, then drew a short line on the alcove ledger. “One string. I’ll pay one. You’ll help carry the next face from the carpenter.”
Yan slid one string onto the desk. “Agreed.”
“Now write down what happened.”
Yan opened his notebook to the practice record and noted the board’s source, material, strike line, and fracture. He wrote that the method’s internal strain had again resolved into stronger marrow, while the old skin cut had tugged when his hand brushed the rough edge. He also recorded that the frame held and the target face split. Gu checked the description, then signed the observation beneath it.
At closing, Yan returned the second-shelf key. Gu locked the cabinet and placed the key on its ring. Yan carried his technique notebook home inside his coat, the warning folded over the copied sequence.
Ning was sorting dried greens at the table when he arrived. She raised her eyes to his bandage. “They let you strike again?”
“One strike. It was the new face, with Gu there.” Yan set down the notebook and showed her the cloth. “The skin pulled when I brushed the board, so we stopped.”
“Did the marrow work as before?”
“Warm and strong. The target cracked. My hand still needs time.”
She returned to the greens. “And the key?”
“Gu let me use the next shelf of damaged texts. I have to record the source, full method, expected benefit, and its internal cost before I activate anything.”
“That sounds like more writing.”
“It is.”
“Will you show me the next manual before you try it?”
“Yes. This Ashen Marrow method was complete once Gu corrected the release point. It works as written now, and the strain changes for me. That doesn’t mean another damaged art will behave the same, or that it would do this for someone else.”
Ning picked a stem from the pile and snapped off its dry end. “I’ll read it with you. Then I can ask what the words mean before you decide whether to practice.”
“I’d like that.”
She nudged a bowl toward him. “Start by deciding whether you can cut these without using the sore hand.”
Yan sat and began sorting with his left hand. “That’s a safer experiment.”
“It also gets dinner made.”
As the evening light thinned, they worked through the greens one handful at a time. Ning asked him to repeat the difference between the cough tonic and the marrow method. He answered while she tied the bundles for the next day. The tonic had soothed a symptom. The manual moved qi and carried a danger inside its own route. She made him explain what the warning meant for an ordinary person, and he did not shorten the answer.
Later, Gu carried the replacement slab to the alcove alone. He set it in the frame and struck it with the wooden mallet twice. The new face held. He checked the braces and called Yan back from the doorway.
“One final controlled blow,” Gu said. “Then we mark the target out of service until the carpenter brings a spare.”
Yan checked the new face and set his feet. His wrapped hand still tugged at the cut, so he kept the strike small and centered. The board held for the first instant; then the crack ran from the mark to the lower edge and split the face in two.
Gu laughed and lowered the mallet. “The repair fund survives.”
“Next time, something less temporary.”
“Next time, you help carry the spare.”
Yan looked at the clean split in the board, then at the note in his book allowance ledger. “For half the repair cost, I expect a better slab.”
“You’ll get the same kind. You’ll just help me carry two.”
They stacked the broken pieces where the carpenter could collect them. Yan went home with the copied sequence dry inside his coat, the key back on Gu’s ring, and the smell of cut wood still on his sleeves.