"Moon grass, manifesting pearl powder, silver-leaf mint…"
Snape stared at the list of experimental materials Rock had scribbled in his notebook. After a long silence he set it down, turned to the storage cupboard, and withdrew a black crystal vial.
"Knowledge deficiency makes you too timid even to experiment boldly with ingredients?"
Snape thrust the vial at Rock, voice flat. "Tell me what's inside."
Rock took it carefully and stepped away from the brightly lit workbench. The vial was opaque black—clearly the contents could not be exposed to light.
Snape had handed it over without hesitation; Rock was not about to open it recklessly.
Snape merely raised an eyebrow at the precaution and said nothing.
In the shaded corner Rock uncorked the vial. First he confirmed the potion showed no violent reaction, then he sniffed it.
Hmm?
The scent was odd—sharp, faintly metallic. He tipped out a single drop. Even with his back to the light the liquid shimmered with its own soft fluorescence and carried a faint fishy undertone.
It was not black at all, but a deep inky blue-green.
He resealed the vial and returned to the workbench. "Professor, this is moonstone powder ground to an extreme fineness, then combined with boggart bile extract."
"Why boggart bile extract?"
Snape's tone was ice.
"The inky-blue hue. If the moonstone powder is correct, only boggart bile extract produces that exact shade." Rock answered steadily.
"Hmph. At least your skull still has room for a few facts."
Snape snorted, replaced the vial, and continued coldly, "Now do you understand why I said your experiments lack even the courage to be reckless?"
"I do, Professor." Rock nodded. "The materials I chose are nowhere near optimal. Compared with the two you just showed me, they're already inferior."
"Magic perception—what exactly is it like?" Snape's voice remained cold, though the usual drawl had vanished. "And how many people have you told about this ability?"
"Professor, so far only you know."
Rock glanced up at Snape, then began to describe the sensation in detail.
Snape listened, brow faintly furrowed. His fingers, clasped behind his back, unconsciously rubbed together. His dark gaze stayed fixed on Rock for a very long time.
"Drink this."
After what felt like an age, Snape returned with a second vial containing a liquid the pale green of new spring leaves.
Rock looked at the faintly glowing potion, tipped his head back, and swallowed without hesitation.
Bitter wormwood flooded his tongue. He couldn't help a slight frown.
"Wormwood extract?"
"Begin processing the ingredients. While I brew I will question you." Snape lifted his chin, motioning Rock to work.
Rock understood at once. The wormwood would blur the boundary between waking reality and subconscious thought; Snape clearly meant to test whether the magic-perception ability remained clear even under its influence.
The result was… satisfactory.
Rock's hands never faltered. Every movement stayed precise and unhesitating.
When he finished the prep work he moved to Snape's side of the bench and watched.
Snape pointed to another crystal vial. "Tell me what this is."
Rock picked up the murky deep-blue liquid, swirled it under the lamplight, then sniffed. "Sopophorous bean, Professor. This is a sedative base."
"Ten seconds. Explain why a sedative that should be vivid violet is now this colour."
"The sopophorous-bean juice extraction was impure, or the unicorn hair was added too early. Given the murkiness, the juice extraction is the more likely culprit." Rock answered calmly.
"Then give me one reason why I have not simply discarded the entire batch."
Rock lowered his gaze to the vial. Through his magical perception the potion's magical threads carried an extra layer of information—something he had sensed before in the Calming Draught Madam Pomfrey once gave him.
"From both the colour shift and my perception, this batch has developed a secondary effect. It can still function as a sedative, though the dosage would need careful calibration. The scent is faint but could also serve as a base for an incense fumigant."
"As a sedative you would need three-tenths more than the standard dose because the potency is noticeably weaker," Snape said coldly. "For fumigant base, one single drop is more than enough."
"Yes, Professor."
Rock pulled out his notebook and began writing at once. These finer points were clearly beyond his current precision.
"It seems your so-called magic perception is not mere boasting." Snape set down his stirring rod, voice low.
He had always wondered how Rock could identify potions after only a few brews or observations—especially the way the boy always took the finished vials and examined them so intently.
Only now did Snape realise Rock had been reading the magical threads inside.
"This matter—no one is to speak of it."
Snape's voice dropped to a near whisper. With a flick of his fingers a sheet of parchment flew into Rock's hand.
Ocular Alchemy (Restricted Section No. 743)
Authorised Borrower: Severus Snape
"Go to the library. Tell Madam Pince you wish to borrow this volume and that… I have permitted it."
Snape's expression never changed. He reached aside again and produced a second book—Potions and Biological Tissue Fusion Studies. "My own revisions are inside. Remember—if you dare show this to anyone except yourself…"
"And if you attempt any of the procedures without supervision, I will personally administer the Forgetfulness Potion."
Rock's eyes lit up. This was real direction. The title alone told him the book was exactly what he needed. Restricted Section—perfect.
"Furthermore," Snape continued, "if you can submit a twelve-inch essay on Lizard-Eye Regeneration Magic and Magical Contamination before next week, I may allow you to observe the brewing of another… unique potion."
"Remember my standards. You know perfectly well I do not want simple regurgitation or copied text."
"Understood, Professor."
Rock met Snape's gaze and answered without hesitation.
Snape decanted the finished potion into a fresh vial, then said coldly, "Well? Do you feel the detention time is too short and wish me to extend it?"