Sebastian found him in the library the next morning, dropping into the seat across from him without invitation.
"I know somewhere we can practice," Sebastian said. "Somewhere private. Ominis and I have been using it since first year for dueling, and no one's ever found us there. Anne too, before she stopped coming to watch us hex each other." He leaned forward, elbows on the table, voice dropping below the ambient murmur of students studying nearby. "Meet me tonight. Nine o'clock, bottom of the Defence Against the Dark Arts tower, near the big horned skeleton on the ground floor. Don't tell anyone. Ominis would have my head if he knew I was even considering bringing someone else."
"All right," Rowan said.
"I'll talk him around before tonight. He'll grumble, but he'll come." Sebastian stood and gathered his things, and that crooked smile surfaced briefly. "See you then, Ashcroft."
The Defence Against the Dark Arts tower was quiet at nine. Rowan found the skeleton easily, a large horned creature mounted against the wall, its empty eye sockets staring down the corridor. Sebastian was already there, leaning against the wall beside it, and behind him stood Ominis Gaunt, pale and composed, his clouded eyes fixed on nothing. His wand was held loosely at his side, its tip emitting a faint directional pulse that Rowan recognized as a navigation charm of some kind. Adapted wandwork for moving without sight.
"Ashcroft," Ominis said. His voice carried the careful enunciation of old wizarding families, measured and precise, shaped by generations of people who expected to be listened to. "Sebastian has spent the last hour explaining why I should allow this. I'm not entirely convinced, but I trust his judgment on dueling matters, if nothing else."
"I appreciate it," Rowan said.
"Don't appreciate it yet. If this goes badly, I'll hold both of you responsible." Ominis turned his head toward Sebastian. "Go on, then."
Sebastian placed his wand against what appeared to be an ordinary section of wall and pressed. The stone shimmered and folded inward, revealing a magical cabinet set into an alcove. He opened it and gestured for Rowan to follow.
The cabinet opened onto a passage that descended steeply, rough-hewn steps spiraling into warm, dry air. Ominis took the stairs with the ease of someone who'd walked them hundreds of times, his navigation charm unnecessary in a space he knew by memory. The staircase opened into a wide vaulted chamber, and Rowan stopped.
The space was larger than he'd expected. Vaulted ceilings supported by thick columns, stonework carved with symbols Rowan didn't recognize. Torches lined the walls, already lit, their flames steady and smokeless.
The center had been cleared into an open area with training dummies along one wall, and a corner had been furnished with mismatched chairs, a table, and a trunk.
"We call it the Undercroft," Sebastian said, watching Rowan take it in. "Knowledge of this place has been in Ominis's family for generations. He showed Anne and me when we started at Hogwarts."
"We used to play Gobstones down here," Ominis said, settling into one of the chairs with the practiced ease of someone returning to a familiar seat. "Before Sebastian decided the space was better suited to setting things on fire."
"Dueling practice," Sebastian corrected.
"The distinction is lost on the training dummies." Ominis's tone was dry, but not pointed. An old complaint, worn comfortable by repetition.
A door at the far end of the passage opened, and Anne Sallow came down the last few steps carrying a tea tray. She set it on the table and looked at Rowan with a warmth that was immediately distinct from her brother's sharp energy. Sebastian watched people the way he watched opponents, calculating angles and openings. Anne simply looked at them.
"You're Rowan Ashcroft," she said. "I've been hearing your name for two years now. It's good to finally meet you properly."
"Likewise."
"Sebastian tells me you learned nonverbal casting over Christmas break and he wants you to teach him." She poured tea into mismatched cups she'd clearly collected from around the castle. "I told him that if he's going to learn this difficult a thing, he should do it somewhere comfortable, with tea. He disagreed. I brought the tea anyway."
Sebastian was already in the center of the practice space, wand drawn, restless with the particular impatience he got when there was a skill in front of him and the learning hadn't started yet. "Are we going to talk, or are we going to do this?"
Rowan set down his tea and walked to meet him.
"Cast a Lumos," Rowan said.
"Lumos." Bright and steady.
"Hold it." Rowan glanced at Ominis and Anne, including them. "I explained the theory to Sebastian already, but the short version is that the incantation does two things: it triggers the spell and shapes the intent. Without it, you need to do both yourself." He turned back to Sebastian. "That's the theory. Now for the practice. There's a pull that gathers in your chest right before a spell fires. The magic starts moving before the word reaches your lips. I need you to feel that pull as separate from the word."
Sebastian frowned, concentrating. The light wavered slightly. "I feel it. Right before it releases. Like a tension."
"That's it. Now end the Lumos and try again without the word. Don't think Lumos, don't think any incantation at all. Just look at the tip of your wand and want light. Think about what accidental magic felt like as a child, if you can remember it. Pure intent with no structure. You wanted a thing badly enough and your magic responded."
Sebastian raised his wand and stared at the tip. His jaw tightened, the same focused intensity he brought to the dueling platform channeled now into the effort of making something happen through will alone.
Nothing happened.
He tried again. Harder, his knuckles whitening around the grip, his arm rigid. Still nothing.
"You're trying to force it through the same pathway it uses when you speak," Rowan said. "That pathway is closed without the incantation. You need to find a different one, and forcing won't get you there. It's the opposite of how you normally cast. Instead of pushing the magic out, you have to let it come."
Sebastian lowered his wand. The frustration was obvious and undisguised. "That's the least helpful thing anyone's ever said to me. Let it come. What does that even mean?"
"It means I sat with my wand for forty minutes before I managed to produce anything at all. Forty minutes of nothing, and then a light that barely flickered. There's no shortcut through the frustration. You just have to stay in it until the shift happens."
Sebastian looked at him for a moment. Then he raised his wand again. This time the rigidity left his arm. He stood with his eyes on the wand tip, searching rather than forcing, and the chamber went quiet around them.
Ominis sat in his chair with his head tilted slightly, as if listening for frequencies beyond the range of ordinary hearing. Anne sipped her tea without comment. The torches crackled softly.
Five minutes passed. Ten. Fifteen.
At twenty-three minutes, a faint shimmer appeared at the tip of Sebastian's wand. A ghost of light, barely there, flickering for a heartbeat and gone.
Sebastian's eyes widened. "I didn't say anything. And that happened."
"Try again," Rowan said.
He tried. The shimmer came back, stronger, lasting a full second before it vanished. Sebastian let out a breath that was half disbelief and half exhilaration. "I can feel where it is now. Like trying to grab a thing in the dark—I know where it is but I can't get a proper hold on it."
"That's exactly where I was after my first session. It comes with repetition. Your mind is building pathways it's never used before, and that takes time."
They worked for another hour. Sebastian produced the shimmer four more times, each one slightly more defined, none lasting more than two seconds. When Rowan finally called a stop, Sebastian was breathing hard and sweating despite the cool air of the chamber.
"Tomorrow night," Sebastian said, and it wasn't a question. The frustration hadn't left his face entirely, but it shared space now with the particular look of someone who'd touched the edge of a real thing and intended to get back there as quickly as possible.
"Tomorrow night. The more consecutive days you practice, the faster the pathways build."
They climbed the stairs together. Ominis replaced the ward on the entrance with a practiced gesture. At the top, before they parted ways, Ominis turned toward Rowan.
"Sebastian doesn't share the Undercroft," Ominis said. Quiet and direct, with a weight his earlier dryness hadn't carried. "In two years, the only people who've set foot down there are Anne, Sebastian, and me. He argued with me for an hour tonight because he believed this was worth making an exception. I'd prefer not to discover he was wrong."
"He wasn't," Rowan said.
Ominis held his sightless gaze on Rowan for a moment longer, listening for whatever it was he listened for. Then he nodded once and walked away toward the Slytherin dungeons.