The dormitory was down a corridor deeper inside the common room. The door was thick oak, marked with a single letter.
"A."
Regulus Black pushed it open.
The room beyond was spacious, four four-poster beds set in the corners with dark green hangings. Each student had their own desk area. From the windows, the Black Lake stretched out like a sheet of ink.
Two boys were already inside.
Cuthbert Avery sat on the bed by the window, lining up his stationery with the sort of care that looked effortless. Blonde hair, blue eyes, chin tipped just slightly upward. When he saw Regulus, he gave a minimal nod.
"Black."
"Avery."
On the bed farthest in, another boy sat with a copy of Curses and Counter-Curses in his hands. Black hair, pale face, shadows lingering under his eyes like he hadn't slept properly in a week.
Hermes Mulciber glanced up once. His gaze was dark and unreadable, but he still inclined his head in greeting.
Regulus set his trunk on one of the empty beds and began unpacking. Books went onto the shelf in timetable order. Quills and ink were placed neatly on the desk. Robes were hung in the wardrobe.
The door opened again.
The fourth boy stepped in, brown-haired with gray eyes and a mild expression. His robes were tidy, though not flashy.
Alex Rosier. A branch of the Rosier family, with parents who worked low-level posts at the Ministry of Magic. Not as influential as the main line, but still pure-blood.
"Hi," Alex said, voice gentle. "I'm Alex Rosier."
Avery glanced at him and gave a cool nod. "Avery."
Mulciber didn't look up.
Regulus said, "Regulus Black."
Alex smiled, set his trunk on the last empty bed, and began unpacking. He was directly opposite Regulus.
The air in the room felt… careful.
Regulus watched anyway, quietly sorting the pieces into place.
Avery was the proud pure-blood core, the sort who wore his bloodline like a badge. Mulciber had the look of someone who lived half in the shadows and preferred it that way. Alex sat on the edge of that world, polite and mild, a pure-blood who hadn't grown teeth from it.
Avery's eyes slid to Regulus. "Back in the common room, you made Travers look stupid."
Regulus didn't turn. "He managed that himself."
"His uncle's in the Department of Magical Law Enforcement," Avery said. "Not a small position."
Regulus's tone didn't change. "And?"
Avery's mouth twitched, amused, and there was something in his eyes that said I get it.
"So," he said, "well done. The Travers family's always acted like they're better than everyone else. Funny thing is, who doesn't know their mess?"
Regulus turned then, meeting his stare.
Avery leaned back against his pillows, as relaxed as if they'd been friends for years. "My father says Slytherin needs new blood this year. People with real ability, not idiots who can only show off their family tree."
His gaze sharpened on Regulus. "You don't look like an idiot."
"What about you?" Regulus asked.
Avery blinked. "What?"
Regulus repeated it, calm as ever. "Are you an idiot?"
Alex, who'd been sorting his things quietly, paused and lifted his head, watching without saying a word.
For two seconds, Avery held Regulus's eyes. Then he said, evenly, "You'll find out."
Regulus nodded once. "Looking forward to it."
Mulciber spoke for the first time, voice low. "That thing you did… knocking a wand spell away. How'd you do it?"
Every gaze in the room shifted to Regulus.
"Protego," Regulus said. "With a bit of technique."
"What technique?" Mulciber pressed.
Regulus didn't answer that. Instead, he asked, "You can cast Protego?"
Protego was not a first-year trick. It took control and intent, the kind you usually didn't see from children who were still struggling to keep a feather hovering without it wobbling.
Everyone in the room came from pure-blood families. They all knew what it meant for a first-year to do it cleanly. They also knew it didn't happen overnight.
Mulciber went quiet. The way he looked at Regulus changed, but it wasn't awe. It was assessment, with suspicion threaded through it.
Alex sucked in a breath. "My dad said only a handful of people at the Ministry can cast it properly."
Avery's stare sharpened. "My father said—"
Regulus cut him off. "Why don't you say what you think?"
Avery froze like he'd been slapped.
His mouth opened, but nothing came out.
What was he supposed to say?
No one had ever asked him that.
In the Avery household, his father's opinion was law. In pure-blood gatherings, elders set the rules of reality. Even in Slytherin, older students' experience was treated like scripture.
Avery had learned to borrow authority. To quote it, repeat it, hide behind it.
And now, with one question, Regulus had peeled it off him like a cloak.
Something hot and unfamiliar crawled up Avery's spine.
Shame.
He realized he'd been using his father's name as armor—and the boy in front of him had seen straight through it.
Avery inhaled, steadying himself, forcing his chin higher like he could hold himself up that way.
"Protego needs precise control," he said, and his voice wasn't as smooth as he wanted it to be. "And clear intent. The first comes from practice. The second comes from will."
He swallowed, kept going anyway. "Most first-years can't even keep a feather floating without it shaking."
His eyes stayed on Regulus. "So you're not most first-years."
Regulus nodded, accepting that.
"Then you aren't either," he said.
Avery blinked.
"If you can see that much," Regulus went on, "you've got judgment. You're paying attention. That's not nothing."
For a beat, Avery looked like he didn't know what to do with that.
Then he let out a short laugh, like he'd surprised himself, and shrugged, sinking back against the pillows again. "Fine."
Across the room, Alex Rosier had been holding his breath the entire time. He looked from Regulus to Cuthbert, wide-eyed with confusion and a twist of unease.
In Alex's home, in that careful, courteous Rosier branch that never stepped out of line, nobody spoke like this. Not so direct. Not so sharp.
He admired Regulus's calm.
He also found it unsettling.
He doesn't feel eleven, Alex thought, watching Regulus with the vague dread of realizing someone your own age is moving through the world with a completely different set of rules.
He feels like… like those department heads at the Ministry who walk fast down the halls and never waste a word.
Tonight, he decided, he was writing to his parents. He wanted to know what was going on with the Black family's second son.
The room fell into silence.
---
Hogwarts's first class for the Slytherin first-years was Potions.
In the wizarding world, Potions was a kind of measuring stick: how careful you were, how precise, how patient. Slytherin liked to pretend those were its natural virtues. At the very least, that was the story.
The Potions classroom was in the castle's lower levels, a little higher than the Slytherin Common Room but just as cold. The air had that damp stone bite to it, laced with old fumes and something herbal that never quite faded.
By the time Regulus stepped inside, most of the students were already seated. Long tables were lined up in neat rows. Each station had two cauldron stands, a basic tool set, and a pile of ingredients waiting like a dare.
He checked the seating chart. Slughorn had clearly put thought into it.
Slytherin and Gryffindor shared the lesson, but the seats were interwoven instead of split. Either it was meant to encourage house unity, or it was meant for entertainment.
Regulus's seat was in the third row.
His partner was a Gryffindor girl with blond hair and freckles. She was flipping through Magical Drafts and Potions.
When he sat down, she looked up, eyes brightening. "You're Regulus Black?"
"I am."
"I'm Mary Macdonald." The words spilled out quickly. "I heard yesterday on the train you made James Potter's spell vanish."
News traveled fast.
Regulus nodded once, leaving it there.
Mary practically lit up at the confirmation. "You should've made James Potter vanish too. I've heard they're awful."
Regulus blinked, a little surprised.
So James already had a reputation. And if that was true, Sirius had probably helped build it.
Mary didn't say more with Regulus right in front of her, but the point was clear enough.
Even Gryffindor students were starting to get sick of it.
She looked like she wanted to ask something else, but the classroom door swung open before she could.
Horace Slughorn swept in.
He was round and rosy, dressed in a dark green robe heavy with gold embroidery, the buttons over his stomach pulled tight like they were under protest. His presence filled the room the way perfume did: loud, rich, impossible to ignore.
"Ah! Welcome, welcome!" Slughorn boomed, all theatrical warmth. "Welcome to the world of Potions, the most delicate, most dangerous, and most rewarding of the magical arts!"
He reached the front, planted both hands on the desk, and beamed at them as if he'd personally invited each student.
"I am Horace Slughorn, your Potions master," he announced. "And for the next seven years, or at least until you've taken your O.W.L.s, I will be guiding you through the wonders that can be found in a cauldron."
His eyes drifted over their faces, lingering here and there as though he were taking notes.
"Some of you may have heard of me," he went on, smiling wider. "Some of you may have heard of my… little club."
A ripple of interest stirred through the room.
"But I assure you," Slughorn said, voice bright, "in my classroom, what matters is your skill and your focus. Most of all, your love for the craft."