Back in the dormitory, seated at his desk, Regulus gently ran his fingers over the cover of Professor McGonagall's notebook.
He flipped through a few pages. Just as she had said, there were no concrete spells inside, only dense reflections on the essence of Transfiguration.
One section discussing gradients of difficulty in material transformation caught his attention.
Professor McGonagall argued that the difficulty of Transfiguration was not determined solely by an object's complexity. It was far more closely tied to the inherent stability of a material's internal structure, as well as the strength of its "form memory."
Combining today's discussion with his own experiments, Regulus found himself arriving at a fairly solid conclusion.
Transforming elemental substances was harder than changing one complex compound into another, especially when the transformation involved a fundamental alteration of the material's original properties.
Turning a wooden stick into an iron rod meant converting one established organic structure into a metallic crystal structure. In essence, it was a shift from one fixed framework to another fixed framework.
Many young wizards could manage that, even if most only succeeded in altering the outward form.
But transforming graphite into diamond was different. It meant changing one form of elemental carbon into another.
Without altering the base element itself, one had to completely reconstruct its internal connections, or in other words, rearrange its molecular structure, to produce two substances with radically different physical properties.
This demanded understanding and reshaping matter at its most microscopic level, and the difficulty far exceeded ordinary changes of shape.
Regulus took out a small piece of graphite he carried with him and began to practice.
He let his magical perception sink deep into the graphite, trying to pry at the stacked layers within, forcing localized distortions and cross-links to form a tiny region of increased hardness and altered luster.
The process was brutally difficult.
Graphite's loose, layered structure had a peculiar tendency to slip. When magic interfered, entire layers often shifted together, making localized reconstruction nearly impossible.
One careless moment could destroy the overall integrity, reducing it to nothing more than fluffy carbon powder.
He had to exert extraordinarily fine control, like wielding the most delicate carving blade, engraving and welding at the molecular level.
It gave him a deeper appreciation for wizards and magic alike.
Wizards might not have developed a scientific system based on experimentation and mathematics the way Muggles had to understand the world and matter at the microscopic scale, but they were by no means inferior.
Professor McGonagall, with only brief observation, could accurately discern the internal differences between graphite and diamond.
That kind of intuitive perception of a material's essence was something Muggle technology still struggled to approach.
Of course, Regulus himself was a special case. His foundation in basic sciences from a previous life, combined with an unusually sharp magical perception after his rebirth, gave him an advantage.
Professor McGonagall, by contrast, relied solely on experience and magical intuition to reach similar conclusions. The gap between them was measured in decades immersed in Transfiguration.
This also clarified the next step on the path forward.
Transfiguration was not merely about altering form. One had to understand the underlying principles, and ultimately reach the point of changing a thing's very essence.
And alchemy, the legendary kind, the kind represented by the Philosopher's Stone and its pinnacle of achievement, it likely touched upon something far more terrifying.
That went beyond rearranging molecular structures. It probably involved reconstruction at an even more fundamental level.
Turning stone into gold might require altering the number of protons in an atomic nucleus, or at the very least perfectly simulating every chemical bond and macroscopic property of a gold atom.
That was completely outside the realm of Transfiguration. The fact that it could also grant longevity and extend life spoke to the vast power contained within it.
Even Voldemort sought to use it to return from death.
During a pause in his practice, his thoughts continued to wander.
The air itself was filled with elemental substances and compounds. Nitrogen, oxygen, carbon dioxide, water vapor, noble gases.
Yet most wizarding magic, whether defensive spells, offensive spells, or everyday charms, did not deliberately filter or block the subtle changes in these invisible components of the air.
It was not because it could not be done. The difficulty was minimal. It was simply something people instinctively ignored.
Take oxygen, for instance.
A sudden idea surfaced. What if the elemental oxygen in the air surrounding a human body were instantly transformed, through Transfiguration, into another oxygen-based substance the body could not use?
Ozone, for example.
Or conversely, other substances could be transformed into oxygen, inhaled, and then reverted after gas exchange.
Glass fibers, asbestos, radioactive elements. Anything would do.
The key lay in extremely precise identification and instantaneous conversion of a specific elemental substance.
For now, it was only theoretical deduction, but the direction was certainly correct.
While Regulus was immersed in microscopic Transfiguration and dangerous extrapolations, the dormitory door opened, and Cuthbert Avery returned.
He saw Regulus seated at his desk, a small, twisted object hovering in front of him. At the tip of Regulus's wand flowed a fine, tightly condensed light.
It was clearly some form of magical practice.
Transfiguration?
The "hey" that rose to Cuthbert's lips was swallowed immediately.
He considered himself on Regulus's side now and understood that interruptions were unwelcome. He moved quietly to his own bed and set his books down.
Not long after, Alex came back as well, arms full of books, his face relaxed after finishing his homework.
He spotted Regulus and instinctively went to greet him, but the moment he opened his mouth, Cuthbert raised a finger sharply to his lips, shot him a fierce look, then tilted his chin toward Regulus.
Alex startled and clapped a hand over his mouth. Following Cuthbert's gaze, he saw Regulus deep in practice.
He fell silent at once and carefully made his way to his bed, feeling oddly reassured.
Cuthbert still carried himself with that familiar arrogance, but this time he had only stopped Alex with a gesture instead of knocking him down with Petrificus Totalus or Stupefy.
Alex could not help but feel that the atmosphere in the dormitory truly had changed.
Before, Cuthbert had been domineering, Hermes unpredictable and gloomy, Regulus distant and silent, while Alex himself lived on edge.
Now, although the hierarchy was still clear, Cuthbert no longer bullied people at will, and Regulus, despite his strength, was not overbearing.
Alex suspected the change had a lot to do with Regulus's presence and influence.
Thinking of the recent letters from home, his parents had, as always, urged him to study well, take care of himself, and get along with his classmates. There was no need to force his way into the core circles. Staying safe was enough.
Alex felt a quiet gratitude toward Regulus. On the fringes of Slytherin's inner circle, Regulus had, without fanfare, created a space where one could at least breathe.
Regulus noticed his roommates returning and the subtle movements in the room, but he did not let it distract him.
His mind was racing, magic pouring out as he maintained delicate control over the graphite's internal structure.
With Professor McGonagall's demonstration and notes as guidance, Transfiguration based on molecular arrangement now had a clear entry point for him, though putting it into practice still demanded enormous effort.
The last to return was Hermes.
He pushed the door open, bringing in a trace of cold from outside.
His gaze went first to Regulus practicing, then to Cuthbert's faintly provocative gesture of restraint, and Alex's cautious posture.
A nearly imperceptible curl of mockery tugged at Hermes's lips.
He had little regard for Cuthbert's eager submission and even looked down on it.
He had lost to Regulus in the Chief duel and been shocked when his immature magic was effortlessly neutralized, but deep down, his confidence remained intact.
He believed he still had many cards left unrevealed. Those were the true sources of power.
At school, many methods were inconvenient to display.
Outside the castle, in an unrestricted fight to the death, Hermes believed that with the truly dark magic passed down through his family, he might not lack the chance to kill Regulus.
Several spells flashed through his mind, inherited or obtained through secret channels.