chapter 13

Chapter 3: The Numbers That Shape Magic

Year 3 – Seeds of Legacy (Chapters 1–10)

Harry had never considered himself especially good at math. At best, he could do basic sums, and even then, he'd always been far more comfortable on a broom than with a calculator. But from the moment he stepped into the Arithmancy classroom, something felt different. The room itself buzzed with potential energy. Charts covered the walls: spirals of magical frequency, ancient arithmetic symbols, modular circles woven with gleaming golden thread. At the center of it all stood Professor Septima Vector, her wand tucked neatly behind one ear and her robes ink-splotched in places that suggested long hours poring over parchment.

"This," she began, "is the language behind all magic. Not the words you say with your mouth, but the structures that shape how magic behaves. Arithmancy is not arithmetic. It's art. Precision. Prediction."

Harry stole a glance at Hermione, who was practically glowing with enthusiasm. He could already see her scribbling notes, the edge of her quill frayed from eager use. He wasn't sure what to expect—but what came next wasn't hard. It wasn't easy, either. It was… familiar.

Professor Vector introduced name theory first. Harry added the numbers under the letters of his full name. They came to 69. He reduced that to 6. "

Six is the number of equilibrium," Vector announced as she moved through the classroom. "Those with six as their core are often drawn into conflicts where balance is needed. The healer. The bridge. The peacemaker."

Harry stared at his parchment.

Hermione leaned over. "That's you. Or it will be," she said softly, proud and certain. "You're always trying to make sense of everything, even when it hurts."

He blinked, startled by how much it felt like the truth.

"Mr. Potter," Professor Vector called. "Would you mind coming to the front, please?"

There was a flicker of surprise in the classroom—especially from students who hadn't expected Harry to stand out in this of all subjects. He walked to the front slowly, trying not to look like he had no idea what he was doing.

Vector tapped the board, changing the display to a progression of numbers:

3, 9, 27, 81, 243…

"What do you see?" she asked.

Harry didn't hesitate. "Exponential growth. Each number's multiplied by three. Base three magic, probably unstable unless grounded. Too much power if you don't add a stabilizing array."

There was silence for a moment, broken only by the scratch of Hermione's quill. Professor Vector's eyes lit up.

"Correct. And fast." She studied him like he was a new rune that had just revealed itself. "Have you seen this sequence before?"

"No," Harry said. "I just… saw how it fit."

Professor Vector didn't say anything for a long moment. Then, she nodded and turned to the class.

"We will continue reviewing spell matrices. Mr. Potter, stay behind when class ends." When the bell rang, Harry lingered while Hermione hesitated by the door.

"You can go on," he said. "I'll catch up." Hermione nodded, but she didn't leave. Not really. She ducked just outside the door and waited, pretending to organize her bag while she strained to hear.

Inside the classroom, Vector handed Harry a parchment. "I'd like you to consider accessing the advanced Arithmantic resources in the Restricted Theory Library," she said. "With supervision. You're exhibiting what we call theorist-level cognition."

Harry blinked. "That sounds… dangerous."

"It can be," Vector said. "Or it can be world-changing. It depends entirely on your control."

Hermione heard the seriousness in her voice and chewed her bottom lip. She didn't know whether to feel proud or jealous—or both.That evening in the common room, Harry sat at a table with two open textbooks, a parchment of number theories, and his own name chart. Hermione was beside him, rattling off frequency patterns and what-ifs about magical names.

Ron sat nearby, supposedly reading a Quidditch Through the Ages article—but mostly watching them.

"You're still doing Arithmancy?" he asked, voice sharp. "Didn't we already have class today?"

"It's not homework," Harry replied, not looking up. "Just... figuring things out."

"Figures," Ron muttered. "You two doing your little number club now?"

Hermione glanced up sharply. "It's not a club, Ron. It's study."

Ron threw his book down. "Well, excuse me for picking a subject that doesn't require staring at squiggly symbols for six hours a night! Divination might be bonkers, but at least we can laugh when Trelawney predicts someone's going to die dramatically every Tuesday!"

Harry looked over. "You didn't even like the first Divination class." "

At least I'm in it with my mates," Ron snapped. "Instead of getting left behind while you and Hermione become magic prodigies with your secret theories and ancient runes!" The words hit harder than Harry expected. Hermione went quiet.

"Ron," Harry said slowly, "I didn't choose these classes to leave you behind. I just… feel like this is something I'm supposed to understand."

"Yeah, well, hope it keeps you warm when you're drowning in magical maths," Ron muttered, pushing out of his seat and heading upstairs. Harry watched him go. Hermione looked troubled, but didn't speak right away.

"Give him time," she said softly. "Ron's just… insecure. He doesn't know how to say it properly."

"Yeah," Harry murmured, "but neither do I."

Elsewhere in the castle, Professor Vector walked briskly toward the staffroom. She knocked once and stepped in. Dumbledore sat near the fire with McGonagall, a steaming cup of tea in each of their hands.

"Septima," McGonagall said warmly. "How was the first week?"

"Promising," Vector said shortly. She handed a folder to McGonagall.

"But I wanted to bring this to your attention early."

Dumbledore opened the file. Inside was a single page: Arithmantic aptitude summary,