The first week of December passed in an eerie calm. The Christmas spirit in the castle gradually grew stronger; garlands of holly and mistletoe hung in the corridors, and even the suits of armor wore ridiculous Christmas hats. Yet the warmth of the holiday seemed utterly unable to penetrate within three feet of Snape.
He was quieter than ever, and even more inscrutable. Apart from necessary classes, he spent almost all his time in the laboratory within the Room of Requirement. But Lin Yanqing keenly noticed a subtle shift in Snape's research focus. He was still improving the Wolfsbane Potion, but he devoted more effort to studying Magical Solvents and detection spells with highly corrosive, concealing, or penetrating properties. Several detailed sketches had appeared on his workbench, depicting the terrain around the Whomping Willow and the castle's underground pipe network, inferred from certain ancient books.
He was preparing to enter the Shrieking Shack. Calmly, meticulously, but with unwavering resolve.
Lin Yanqing did not try to dissuade him directly again. He knew that would only provoke stronger defiance from Snape. He chose another approach—joining in.
He was no longer merely an assistant who handled ingredients and passed over tools. He began taking a more active part in these "preparations." He would point out observation blind spots that might have been overlooked on a sketch, use his Ravenclaw status to borrow obscure books from the edge of the Restricted Section concerning changes in the castle's structure—under the pretense of researching ancient magical fortifications, of course—and even offer suggestions for improving detection spells based on the limited knowledge the system provided about detecting magical traps.
His involvement was technical, without any emotional inclination, as though this were simply another necessary branch of their dangerous research. That attitude actually made it easier for Snape to accept. A strange pattern of cooperation formed between them: Snape was the chief planner and primary executor of the revenge operation, while Lin Yanqing became his tacitly acknowledged "logistics officer," providing technical support and risk analysis.
Ding-dong! (?-?) System analysis: The contract target's obsession level continues to rise. Intent to engage in dangerous behavior confirmed. Auxiliary mission issued—[Frost Trace]!
Mission Description: Provide basic safety measures for the contract target's "expedition." Create a set of simple magical warning marks. Mission Requirements: Create and place at least three concealed marks with magical sensing functions together with the contract target. Mission Reward: Environmental Concealment Dust (small area, short duration) x1, System Points +30. Failure Penalty: None. (System Cub shrugging emoji: "After all, the host is already trying very hard to cover for him~")
That evening, while Snape was once again frowning at a sketch of the Whomping Willow's root structure, Lin Yanqing took out several evenly textured Dwarven Cast Iron Slices exchanged from the system, along with some specially prepared magical etching fluid.
"Perhaps we can place these along several possible routes." He pushed the materials toward Snape, his tone as flat as if they were discussing the proportions of potion ingredients. "The simplest Warning Runes, attached to metal, buried in the soil or set into cracks between stones. Any creature with strong magical power passing by will make them heat up slightly and send faint fluctuations to the primary rune plate I keep here. At the very least... it could give you a few more seconds to react."
Snape stared at the iron slices, a sharp gleam flashing through his black eyes. Of course he understood what this meant—Lin Yanqing was not merely providing technical support; he was also laying out an escape route for him. It was a silent declaration: I cannot stop you, but I will do everything I can to keep you from dying in there.
He silently picked up an iron slice, his fingertips feeling its icy surface. He neither thanked him nor refused. Taking up the etching knife beside him, he began precisely carving the simple diagram Lin Yanqing had provided into the metal. His movements were swift, carrying a suppressed ferocity, as though he meant to pour all his resentment and rage into the cold metal.
Lin Yanqing also picked up his tools and worked on another iron slice. The only sound left in the laboratory was the soft hiss of carving blades scraping over metal. This cooperation was entirely different from brewing potions together in the past. There was less love of creation and more cold preparation for confronting destruction.
Just as they were absorbed in their work, an extremely faint, almost imperceptible sound came from outside the laboratory door—outside this space formed by the Room of Requirement, a place that should theoretically have been completely private. It sounded like something soft, perhaps the hem of a robe, brushing against the stone door.
Both of them froze at the same time and abruptly looked up. Their gazes met in midair, and each saw the vigilance in the other's eyes.
Like a startled venomous snake, Snape silently slipped to the door, wand already in hand, and pressed his ear close to listen. Outside, there was deathly silence, broken only by the faint sound of wind drifting from somewhere far away in the castle.
Lin Yanqing held his breath as well, feeling through the contract the intensely taut wariness radiating from Snape. Instinctively, he tightened his grip around the [Environmental Concealment Dust] that had just been awarded by the mission in his pocket.
A few seconds later, Snape slowly stepped back and gave Lin Yanqing an almost imperceptible shake of his head. There was no one outside.
But that feeling could not have been wrong.
Someone had lingered outside the door. Or rather, something had tried to spy on this secret laboratory.
Snape's expression darkened further. He returned to the workbench and looked at the unfinished warning plates, a cold curve tugging at the corner of his mouth.
"It seems we aren't the only ones interested," he said quietly, his voice carrying a trace of offended anger and deeper vigilance.
Lin Yanqing's heart sank as well. The eyes that had watched Snape on the night of the full moon seemed to be... closer to them now. Whoever it was not only knew about Snape's actions that night, but might even have suspected—or discovered—the existence of their secret laboratory.
Before, the conflict had been limited to them and the Marauders. But now, an unknown force hidden in the darkness seemed to be quietly closing in.
Snape's plan had yet to be carried out, but they could already seemingly feel an invisible net slowly tightening. Across the frostbound tracks fell a shadow from the darkness, carrying malicious intent.
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