Harry Potter: The Book of Sin

"Found it!" Maca couldn't help but feel pleased at having quickly located the information he was looking for.

He read line by line, word by word, silently mouthing the words to himself:

"Fairies, Magical Creature Classification: XX. Fairies carry wands that resemble tree branches..."

That very afternoon, Maca eagerly opened one of the books he had ordered—The Book of Potions, a classic potionology text. It was a rare volume published in the 16th century, and had he not come across it on an old booklist at Flourish and Blotts, he might have missed it entirely.

While flipping through its pages, one entry caught Maca's eye—a rare potion ingredient: fairy wings.

These were considered exceptionally rare. While losing their wings wouldn't kill fairies, their inherently vain nature made it unthinkable for them to allow anyone to take them.

"…Fairy wings possess unique magical properties. They can shimmer dazzlingly when the fairy wishes to draw attention, or cloak her presence when she wishes to hide."

Maca found himself speculating:

"If I could use these wings as the primary ingredient, perhaps I could brew a truly special invisibility potion."

The concept of invisibility had always fascinated him. Apart from the complex craftsmanship of Invisibility Cloaks and the high-difficulty Disillusionment Charms, only a few potions were known to grant true invisibility to an adult wizard. Unsurprisingly, these potions were extremely expensive—mainly due to the rarity of certain ingredients.

This led Maca to a bold, perhaps unrealistic idea: Why not try to develop a new invisibility potion himself?

He knew it was a long shot, but saw it as a personal challenge—an opportunity to create something new.

Maca had always believed that opportunities weren't given—they were made.

"Excuse me, do you know where I can find books on how to cultivate valerian?"

Just as he was about to return the book to the shelf, he heard a quiet voice behind him.

The voice was so soft that he almost thought he imagined it. Just to be sure, he turned around to check.

"Uh, did you just say something?"

Standing quietly behind him was a petite girl, wrapped tightly in an oversized Slytherin robe. A wide-brimmed, pointed hat sat atop her head, casting a shadow that concealed most of her face. All Maca could see were her small, rosy lips.

"Excuse me, do you know where I can find books on how to cultivate valerian?"

She repeated the question exactly, her tone flat and emotionless—reminding Maca of Professor Binns from History of Magic.

"Uh, yeah... the herbology section should be over there."

He instinctively pointed to a nearby bookshelf across the aisle.

No sooner had the words left his mouth than the mysterious Slytherin girl turned and walked off without so much as a "thank you."

"What was that about?" Maca stared dumbfounded at the girl's retreating figure, feeling utterly ignored.

It was as if, in her eyes, he was no different from a tree by the roadside—something that didn't warrant the slightest attention.

Tilting his head thoughtfully, Maca tried to recall if he'd ever seen this enigmatic Slytherin girl before, but came up empty.

"Well, whatever. I'll ask around later. She must be a first-year like me, right?" he muttered, shaking his head before heading toward the Potions section of the library.

He figured he'd probably be coming to the library more often now—its collection was nothing short of astonishing. There was bound to be some major discoveries waiting if he searched thoroughly enough.

Over the next few days, aside from attending classes like everyone else, Maca spent nearly all his free time holed up in the library on the fifth floor.

Most students who visited the library during that time would encounter a familiar sight:

Near the bookshelves for Potions and Herbology, there was always a long reading table almost buried beneath a mountain of books. These weren't just any books—they were advanced theoretical texts, usually only borrowed by upper-year students or even professors.

Madam Pince, the strict librarian, kept a hawk-like watch over this particular table, as if the person sitting there were trying to desecrate her children. Her eyes were sharp, practically brimming with silent rage.

To find out who was actually sitting there, you had to circle around to the back—because from the front, the view was completely blocked by the towering stack of books.

Without meaning to, Maca had become something of a topic among the Hogwarts student body.

Not just because of his conspicuous presence in the library, but also because he was the only non-Slytherin student who could hold a semi-civil conversation with Professor Snape without getting immediately ridiculed.

Even the ever-diligent know-it-all Miss Granger couldn't manage that, despite her excellent grades in Potions.

"That's just because Hermione's in Gryffindor," Maca had replied with a shrug when Ernie brought up the rumor.

As a student, Hermione was undoubtedly brilliant—Maca fully acknowledged the immense effort she put into her studies. But even so, he didn't believe in her all-encompassing, scattershot approach to learning. It simply wasn't the right method for a wizard.

The more deeply he studied, the more convinced he became—magic was vast and profoundly complex. Just mastering Potions alone could very well take a lifetime.

…

When a person is fully immersed in something, time flies.

Before he knew it, a week had passed.

During that time, Maca hadn't run into the mysterious Slytherin girl again, but his understanding of Potions had soared.

He had fully digested the books he'd ordered and even made major progress on his research into a "new type of invisibility potion."

Regarding how the wings of fairies produced their cloaking effect, Maca had already reached a conclusion. It turned out to be a completely different form of invisibility—unlike the optical illusion created by Invisibility Cloaks or the environmental blending of ancient potions.

This was a third kind: Perceptual Suppression Invisibility.

It didn't actually alter your physical form or appearance, but it made others unable to perceive your presence.

"Amazing stuff… but man, is it expensive!" Maca groaned, slumping face-first onto the table with a heavy sigh.

His calculations showed that, to render a wizard completely undetectable, the potion needed a rather hefty dose of fairy wings.

"One portion of fairy wings costs 8 Galleons, so three portions come to 24… add in other ingredients and catalysts, and a single vial costs 43 Galleons!" He let out another sigh. "That's daylight robbery!"

"…Wait! Why am I even worried about this?" Maca suddenly sat bolt upright, as though he'd made some grand discovery.

"NO NOISE IN THE LIBRARY!" Madam Pince shrieked from across the room.

"…And she doesn't care if she's being noisy," a few nearby Ravenclaw girls whispered to one another.

Maca gave an awkward smile and bowed his head repeatedly in apology before slinking back into his fortress of books.

There was no doubt about it—an effective new potion like this one meant only one thing: wealth.

Compared to the few rare and outrageously priced invisibility potions on the market, Maca's formula was already considered cheap.

In the wizarding world, rare potions were always prohibitively expensive. Potions masters like Snape—who had created or refined several highly effective formulas—were extremely sought-after.

If not for the fact that Snape was entangled in so many complicated matters and clearly had other ambitions, he would've long become a private consultant for some renowned potion-making company or noble family.

So what if he didn't care much for money? Since ancient times, which true Potions Master has ever truly lacked it? As long as he chose the right channels to sell his work, the Galleons wouldn't just trickle in—they'd be more than enough to support further research. When it came to trade, that was where Maca's real strength lay.

Early the next morning, he had Marfa deliver a shopping list. He wanted to begin experimenting with this potion immediately. But before that, there were a few practical issues he had to resolve first.

Knock, knock, knock.

During the lunch break, Maca knocked on a door almost no student would dare approach unprompted—the door to Professor Snape's office, the master of Potions.

"Who is it?" came the cold and gloomy voice from inside, as if to remind the visitor they were decidedly unwelcome.

"Professor Snape, it's me—Maca McLean."

"…Come in." The voice paused briefly before replying.

Maca turned the doorknob and entered the dim, shadowy office. He walked in quickly.

"Professor Snape, I have a few questions about Potions I was hoping to ask. I hope I'm not disturbing you," he said, choosing his words carefully, trying to sound as respectful as possible.

Snape glanced at him expressionlessly and replied with a trace of impatience, "Ask."

"Actually, I ran into a few issues while studying some potion texts. For example, regarding Hestia's Second Law—how should one handle the anti-magic reaction that occurs during brewing, in order to maintain the potion's stable magical form?" Maca nodded politely and got straight to the point.

"Hmph." Snape frowned and gave a cold snort upon hearing that.