Regulus had a rather dangerous idea.
A fatal strike against all carbon-based life, wizards included.
What kind of compound was almost universally lethal to carbon-based organisms, and could be produced on the spot through Transfiguration?
Cyanide.
Whether hydrogen cyanide gas or cyanide ions, both were extremely toxic.
They rapidly inhibited cellular respiration, required only a tiny lethal dose, and took effect with terrifying speed.
The air contained nitrogen and carbon. Water vapor provided hydrogen.
In theory, if one's magical control were absurdly precise, it would be possible to instantly isolate nitrogen, carbon, and hydrogen atoms from the surrounding environment, forcibly assemble them into hydrogen cyanide molecules, and deliver them straight into a target's respiratory system.
That demanded more than control over molecular arrangement.
It bordered on the delusion of atomic-level manipulation, along with real-time elemental identification and synthesis path calculations on the level of a supercomputer.
At present, it was pure fantasy.
But the magical world never lacked miracles that turned the impossible into reality.
At the very least, this line of thought pointed to the heights Transfiguration might reach under extreme conditions.
At that level, it would no longer be a support discipline in combat.
It would become the most concealed and most lethal of weapons.
If struck, a highly skilled wizard might have a chance at emergency self-rescue.
A mediocre one would almost certainly die.
Of course, that was unimaginably far away, perhaps even unattainable forever.
Still, it was a direction worth moving toward.
Hermes struggled to his feet, bracing himself against the bedpost, head lowered, no longer daring to look at Regulus.
The arrogance in his heart had been completely shattered, replaced by deep wariness and fear, along with a trace of twisted curiosity toward that unknown power he did not even realize he felt.
The confidence he once had in overturning the situation through dark magic now seemed laughable.
He needed to reassess everything, himself included, and how he should face this terrifying roommate.
Silence returned to the dormitory. A faint, unreadable smile touched Regulus's lips as he picked up a fresh piece of graphite and began another round of practice.
---
Exploring the essence of matter through Transfiguration was undeniably fascinating, but Regulus knew it required years of accumulation.
It could not be rushed.
Right now, he needed something more immediate and critical.
Defensive capabilities to deal with the looming threat of Voldemort.
Occlumency came first.
The original records mentioned that Severus Snape had relied on this art to act as a spy at Voldemort's side without being discovered by a master of Legilimency.
True mastery of Occlumency did more than defend against Legilimency. It might even help resist the Imperius Curse.
It was an indispensable survival skill when facing Voldemort.
But Occlumency alone was not enough.
He began thinking about passive magic.
Spells that required no active casting to remain effective, or that triggered automatically to protect the caster.
Hogwarts's standard curriculum rarely covered these.
They were often considered advanced or obscure arts, scattered among ancient family legacies or buried in high-level grimoires.
Occlumency was the most fundamental of these passive mental defenses.
For Regulus, entering the restricted section without permission was a matter of zero times or countless times.
Tonight, a Wednesday evening before Halloween, the castle was unusually quiet.
He decided to sneak in again.
The process was routine by now.
He did not linger. His goals were clear. Using powerful mental scanning and reading techniques, he rapidly absorbed and memorized the core content of the relevant books.
He saw many titles:
"The Fortress of the Mind: Essentials of Mental Defense"
"Ancient Warding Rituals and Permanent Magical Imprints"
"The Nature of Magic: On Shaping and Disguising Personal Magic"
"An Introduction to Dark Magic Detection and Countermeasures"
"Soul Resilience: On Resisting Possession and Enchantment"
"The Hidden Path: Tracking, Counter-Tracking, and Magical Obfuscation"
The depth of Hogwarts's library was staggering. It also outlined a vast field of knowledge he would need to explore in the future.
Back in the dormitory, Regulus immediately began practicing Occlumency.
According to the texts, its core lay in strictly controlling the leakage of thoughts and emotions, and constructing complex false structures or rigid mental labyrinths deep within the mind to mislead intruders.
Training progressed through several stages.
First came the basic barrier.
Focus the mind and erect a simple wall at the outer edge of consciousness, preventing surface thoughts from scattering freely or being read.
Next was organization and partitioning.
Different memories, knowledge, and emotions were categorized and stored in separate mental rooms.
Then came false thought generation.
Actively creating plausible but irrelevant or misleading mental fragments that would automatically be pushed forward as bait when an intrusion occurred.
Finally, deep consolidation and automatic defense.
Training the system into instinct, so that even without conscious maintenance, the subconscious would continue running basic barriers and bait deployment.
Only the deepest and most central thoughts would be heavily protected, with access paths rendered extremely complex.
With a mind and soul that had been relentlessly tempered through meditation, already far surpassing his peers and even many adult wizards, Regulus found entry-level Occlumency almost frictionless.
He quickly mastered the construction of basic barriers. His mental partitioning was orderly and precise.
That said, reaching a level capable of fully deceiving a Legilimency master like Voldemort would likely require far more practice and refinement of advanced techniques.
Still, the door was now open. What remained was patience and adaptation.
He even formed a hypothesis. Could the dynamic model of star meditation serve as a special core for a mental labyrinth?
Hide the most critical secrets within constantly running, highly complex stellar calculations.
Even if an intruder breached the outer defenses, faced with a vast, ever-moving starfield that demanded immense computational ability to comprehend, they would likely lose their bearings long before finding anything of value.
Over the next two days, while solidifying his Occlumency, he also began exploring other passive magic.
He understood the prototype of Constant Protego as shaping his own magic, spreading it across the surface of his body as an extremely thin but evenly distributed protective layer.
This required continuous, subconscious micro-adjustments of magic and consumed tremendous focus.
For now, it could only be maintained for short periods.
Danger sense, combined with his already sharp magical perception, became another focus.
He consciously trained himself to notice even the faintest hostility in his surroundings directed toward him.
Every passive spell was difficult to learn and master.
They did not pursue explosive power. Instead, they demanded exquisite control over one's magic and mind, along with long-term, gradual transformation.
But their advantages were obvious.
Once established, they became instinctive, always-on armor and radar, offering early warnings before danger struck.
They provided an automatic buffer when attacked, and protected the deepest secrets when someone attempted to pry.
For someone who needed to maneuver within the dark faction, their importance rivaled that of any powerful offensive spell.
---
Friday afternoon, Potions class ended early.
Regulus headed toward the library as usual, but in a secluded corridor connecting the dungeon classrooms to the main stairwell, he heard familiar jeers and laughter.
James Potter, Sirius Black, Peter Pettigrew, and Remus Lupin, who looked like he was trying to intervene with little success.
They had Severus Snape surrounded.
Snape's robes had been splashed with some kind of sticky potion residue that continued to emit a foul smell. His hair was soaked, clinging to his face.
His expression was dark enough to drip venom. His wand was clenched tightly in his hand, but facing four opponents, especially with James and Sirius flanking him on either side, he was clearly isolated.
"Well, look who it is. Our dear Snivellus conducting another one of his potion experiments?" James jeered loudly. "Planning a new stink attack this time?"
"Let me go, Potter," Snape hissed, the words forced out through clenched teeth.
"Let you go? We're just kindly helping you clean that unidentified filth off your robes. It's really disgusting. Just like you."
Sirius lounged against the wall, wearing that familiar grin filled with rebellion and prankish delight.
Regulus stopped, not stepping forward right away. He simply watched in silence.