The first Thursday of November brought a Scottish wind that found every crack in the castle. A thin layer of frost clung to the corridor windows.
Young wizards had switched to heavier robes, collars cinched tight, necks tucked as they shuffled toward classrooms.
The Charms classroom sat on the seventh floor, windows facing east. When the morning light slanted in, you could see dust motes drifting through the air.
Professor Flitwick stood atop his usual stack of books, beaming as students settled in. He clapped once, and the buzzing chatter died away.
"Two new spells today. Sonorus, and Quietus."
His wand touched his own throat. "Sonorus."
Flitwick's normal voice was high and soft, but now every syllable rang out like a bell. The window glass hummed. A loosely shelved book on the top row smacked to the floor.
Students in the back row clapped hands over their ears, then lowered them, glancing around in wonder.
The professor tapped his throat again. "Quietus."
The sound vanished. A few students cupped their ears and strained. Nothing. They could only stare at each other.
Regulus noticed that Flitwick's throat was still moving. Sound was still being produced. It simply wasn't propagating.
He knew both spells already. Basic as they came, though their applications were broad enough.
Dumbledore used Sonorus every year for his opening address in the Great Hall. Simple to learn. Touch the wand to the throat, speak the incantation, and your voice carried. To stop it, one more incantation, and it stopped.
Nothing complicated about any of that.
Then a thought surfaced.
Sound was a wave. And light was a wave too.
Sound waves were mechanical, requiring a medium. Light was electromagnetic, capable of traveling through vacuum.
Different in nature, different in propagation, but both obeyed certain universal properties of waves.
The kind of thing he'd have skimmed past in a textbook once without a second thought. Too elementary to bother with. But now things were different.
Regulus stared at his wand. The thinking he'd been doing about Light Source Magic tangled with the demonstration unfolding in front of him.
Sound could be amplified, focused directionally, silenced. Could light be controlled the same way? Could the principles behind Sonorus be adapted for light magic?
Around him, the other students were buzzing with excitement. A spell that could make your voice fill the room? Brilliant. A cluster of Ravenclaws leaned together, eyes shining.
"If you used Quietus during an exam," a bespectacled boy whispered, "could you stop the professor from hearing you and your neighbor swapping answers?"
The girl beside him rolled her eyes. "And the professor can't see your lips moving?"
"I could hide under the desk."
"Then you'd better shrink yourself first."
They dissolved into laughter.
A girl in front of them turned around, face perfectly flat. "Has it occurred to either of you that the professor also knows Quietus? Whatever answers you're trading, he can make those sounds disappear too."
"What about haggling in Diagon Alley? Cast Sonorus on yourself, big voice, big presence."
"Better yet, cast Quietus on the shopkeeper so he can't hear your offer."
Several students snickered, each new idea more absurd and delightful than the last.
Flitwick used his wand to write the key points. Glowing letters hovered in midair.
Sonorus: amplify voice, project across the room, wand to throat.
Quietus: reduce or eliminate sound in a designated area.
The difficulty lay in controlling the direction of Sonorus and fine-tuning the volume suppression of Quietus, even cutting sound off at a specific point in space.
"Begin practicing."
The classroom erupted. Cries of "Sonorus!" rang out in every pitch and volume imaginable.
Some voices boomed like thunder. Others came out barely audible. A few wobbled with nerves.
Quietus produced even more comical results. One student aimed at his desk partner and accidentally halved his own volume instead. Another swung a wand so hard it nearly cracked the skull of the person sitting in front.
Flitwick wove between desks, his small frame slipping nimbly through the rows, pausing to correct pronunciation or adjust a wrist angle.
Regulus raised his wand, pressed it to his throat. "Sonorus."
His voice left his mouth and traveled in a clean line to the window on the far diagonal of the classroom. The glass trembled faintly.
That simple. One thought, one destination, and it arrived.
He cast it several times in succession. Then noticed something.
When his amplified voice passed through areas where other students were practicing, there was an extremely faint distortion. His sound wave collided with theirs, producing a subtle warping.
Regulus stopped and stared at the tip of his wand.
Naturally, sound left the throat and radiated outward in all directions. That was basic propagation.
What Sonorus did was use magical energy to guide those sound waves, channeling them in a specific direction. But channeling wasn't the same as eliminating spread. The waves still diffused, only compressed in range, concentrating their energy so they traveled farther and sounded louder.
In physics, that was directional wave propagation. Magic acted as a kind of acoustic lens, bending the sound wave's path.
What if it could be made not to spread at all?
He cast another Sonorus, this time concentrating hard, not only guiding the direction but actively collapsing the beam, narrowing it until it was almost a line.
The sound shot straight at its target with virtually no diffusion. That part was easy enough, a function the spell already supported if you pushed it.
What he wanted to understand was the principle behind it.
How did magical energy interact with sound waves? And could it interact with light waves the same way?
The bell rang.
After afternoon classes let out, the corridors churned with foot traffic. Regulus cut through the crowd and pushed open the heavy oak door of the Library. The hinges let out a low groan.
Madam Pince poked her head from behind a shelf, gave him a look, and retreated.
He walked deeper in. By the window. The corner. The spot with the best light.
Lily sat there, a book spread open, flipping pages.
She looked up at the sound of footsteps. Saw him. Gave him a smile, though her tone dragged a little. "Long time no see."
Regulus caught the edge in her voice and sensed something was off.
He thought about it honestly. Classes, spell practice, experiments in the Forbidden Forest. Every day packed full.
Then he decided nothing was actually off.
He set his book on the table, pulled out the opposite chair, and sat. "Long time no see."
Lily shot him a look but said nothing more, dropping her gaze back to her book.
The book Regulus had brought was on fundamental spell theory. A film of dust coated the cover. The leather had gone stiff, corners curling.
The kind of book no young wizard went out of their way to read. For most of them, if you could wave the wand right and say the words, the spell worked. Why bother learning why?
He opened it and found the chapter on Sonorus.
Sunlight crept through the window, sliding from the corner of the table to its center, then onward to the far edge.
Shadows on the bookshelves stretched from short to long, drifting from one side to the other.
By the time the sun dipped low and the light turned amber, Lily closed her book. Green eyes looked across at him. "You didn't come for over a week. What were you up to?"
Regulus closed his own book. "Practicing magic."
"What kind?"
"Something new. Still testing it."
Lily nodded and didn't push further. If he didn't volunteer details, she didn't chase them.
She changed the subject, a flicker of curiosity in her voice. "I heard about your Defence Against the Dark Arts class."
Regulus looked up.
"Professor Vance had you come up front. You dueled him. You pushed him back."
One corner of his mouth twitched. "Exhibition match."
So word had spread. Among young wizards, this kind of story traveled faster than anything.
Not that it mattered. Influence had to come from somewhere.
Lily didn't respond right away.
When she'd first heard, a jolt of excitement had gone through her, mixed with something warm. Not entirely because Regulus had bested a professor. More because it was someone she knew. Her friend.
Hearing people say he was brilliant produced a feeling she couldn't quite name, but it was stronger than being told the same about herself.
She'd wanted to ask him about it, hear the story from his own mouth, but he hadn't come to the Library for over a week. No chance to ask.
Later, an older student had pointed out that professors wouldn't go all out against a younger wizard. It was a classroom demonstration, nothing more.
She understood that, of course. But the warmth in her chest hadn't cared.
Now, more than a week on, the initial thrill had faded. The curiosity remained.
Multiple versions of the story were circulating. Some exaggerated, some detailed, no two agreeing on specifics.
But one detail was consistent across every telling: Regulus had used nothing beyond second-year spells.
Disarming Charm. Impediment Jinx. Stunning Spell. Transfiguration. Nothing outside the textbook. Yet the way he'd used them bore no resemblance to a second-year's casting.
She thought of the Protego lesson. How Regulus had let her experience what a complete Shield Charm felt like.
She'd practiced for a long time after that. Could cast one now. Not stable yet, but real.
That day had taught her something: the same spell in his hands and in anyone else's were two entirely different things. She'd never been able to pin down exactly where the gap lay.
"That's what I wanted to ask about." Her tone turned serious. "Same spells. Other people's come out limp. Yours come out... I haven't seen it myself, but everyone says the same thing. Fast, precise, powerful. How do you do it? Is it practice, or is there a trick?"
Regulus considered. "Both."
Before she could follow up, he turned the question around. "When you practice a spell, how do you practice?"
Lily blinked. "The way the professor teaches it. Read the book, repeat the incantation until it works."
"And after it works?"
She blinked again, voice uncertain. "Get more comfortable with it... then move on to the next one."
She trailed off and lowered her gaze.
Regulus hadn't done anything. Same posture, same mild expression, same conversational tone as always.
But she felt a prickle of discomfort.
Like something she'd always assumed she was doing well had been turned over and examined. And after the examination, something was wrong. Maybe everything was wrong.
Regulus noticed the shift but didn't comment.
His expression stayed gentle, his voice even. "That's the school method."
He continued: "When I practice a spell, getting it to fire is only the start. After that, I make it faster, more accurate, more stable."
Lily looked up.
"Faster doesn't mean reciting the incantation faster. It means shortening the time between intent and the magic reaching the wand tip. Accurate doesn't mean aiming at the target. It means knowing where the target will dodge and casting ahead of them. And stable means not only keeping the trajectory true after the spell leaves the wand, but keeping the spell itself intact until the moment of impact."
Lily's brow furrowed as she listened.
Regulus smiled. "You said 'get comfortable.' That's only the foundation. Everything I just described is also foundation, but you're at the foundation of the foundation. Get to my level of foundation first, then start climbing."
Lily glared at him, eyebrows up, mouth pressed down, trying to look fierce and failing entirely.
She wanted to say what's that supposed to mean, but the words stalled in her throat.
She studied his face. No mockery. Only the expression of someone stating something self-evident.
A quiet sigh escaped her, and her eyes dropped.
What Regulus said was bound to be right. He'd never been wrong about anything. And he was that good.
She remembered last year, at this same table, when he'd laid out the fundamentals of dueling for her.
Understand the spell. Master the spell. Body movement. Anticipation.
"In a duel, the clash of awareness comes before the clash of spells."
She'd carried those words with her since. Every time she practiced, she'd run through them in her head.
Do I understand this spell?
Where is my body when I cast?
Where will the opponent dodge?
She'd thought that was the whole picture.
Now, listening to him, she realized how much was still missing.
Everything she'd worked so hard at, everything she'd believed put her ahead of others, in Regulus's framework was only the foundation of the foundation?
She hadn't even reached foundation?
Then what did "climbing" look like?
Professors wouldn't teach this unprompted. Textbooks didn't cover it. For Pure-blood wizards, this kind of knowledge was probably unremarkable, passed down casually at home.
But for someone like her, with no one to tell her, she simply never knew. The hours had been spent, but her thinking had never moved in that direction.
Lily sighed. "None of this is anything a professor has ever taught."
No complaint in the words. Only a quiet regret.
Regulus looked at her and said softly, "Professors teach magic. Not how to use it."
Same as always.
Every time she asked a question, it was like this. No matter how basic, no matter how embarrassing, he listened, then explained slowly. Never laughed at her. Never looked annoyed.
She glanced out the window. The condensation on the glass had cleared, and she could see branches swaying in the wind.
After a moment, she spoke. "Do you think I could do it?"
The corner of Regulus's mouth curved up, eyes crinkling. "You're smarter than me. If I can do it, why can't you?"
Lily laughed out loud, throwing him an exasperated look. "Is that a compliment for me or for yourself?"
Regulus smiled at her and said nothing.
Outside the window, the light dimmed. Amber faded to blue-grey. Every shadow on the bookshelves dissolved.
Lily gathered her books. "Time for dinner."
Regulus packed up too. They stood and headed for the door.
At the threshold, Lily asked, "Next time I practice, could I call on you?"
Regulus turned to look at her.
A trace of hope sat in her eyes, edged with uncertainty. "Is that okay?"
He answered with a smile. "Of course. Wanting to improve is always a good thing."
Lily's eyes curved. She exhaled sharply through her nose, a sound that could have been reluctant concession or plain happiness.
She turned around. "Come on. Dinner."