On Friday afternoon, after Runes, he walked the fifth floor corridors differently.
He went slowly. Past the Charms classrooms, past the portrait of the sleeping knight that snored so loudly you could hear it from the stairwell, past the alcove where a suit of armour stood guard over nothing in particular. He was paying attention to the walls, to the feel of the stone under his feet, to the ambient magic that lived in the fabric of the castle.
At the far end of the corridor, past the last classroom, the passage turned left toward a staircase that students used to reach the sixth floor. Rowan had taken that staircase hundreds of times. He'd never stopped at the section of wall where the corridor turned, because there was nothing to stop for. A blank stretch of stone between a tapestry of trolls in tutus and a window that overlooked the courtyard.
He stopped now.
There it was. The same pressure he'd noted in his journal beside the sketch of the dungeon door. Old magic, locked and waiting, pressing outward from behind the stone. He'd been walking through it for two years without ever turning his head to look at it. Now that he was standing still and paying attention, he couldn't understand how he'd missed it.
He reached out and touched the wall.
The stone burned when he touched it. A deep biting chill that had nothing to do with the temperature of the corridor. It seeped into his fingers and up his wrist and he pulled his hand back. His fingertips were white.
He pressed his wand to the stone. A diagnostic charm returned nothing useful, just the dense magical signature of Hogwarts itself, layered so thick that any individual enchantment was lost in the noise. He tried a Revealing Charm. The wall shimmered but held.
He pushed magic into the stone, steady pressure, the way you'd lean on a door to test whether it was locked. The wall resisted for a moment and then something shifted. The stone between the tapestry and the window folded inward, silently, revealing a narrow staircase that climbed steeply upward. The steps were covered in frost. The air that came out of the passage was bitter, far colder than it should have been, and Rowan's breath misted as it hit the threshold.
He climbed. The frost thickened with every step, the walls narrowing until his shoulders nearly touched both sides. Ice had formed along the ceiling in crystalline ridges that caught the light from his wand and threw it back in fractured patterns. The temperature dropped with every step, pressing through his robes, and he cast a warming charm that lasted about thirty seconds before it guttered out.
At the top of the stairs, a door. A wall of ice, floor to ceiling, blue-white and opaque, with a depth to it that suggested it went back further than the eye could reach. The surface was smooth except for a pattern etched into its centre, a shape that might have been a crest or a seal, the lines filled with something darker than the surrounding ice.
Rowan touched it. It burned his skin on contact. He pulled back with a hiss and looked at his fingertips, which had gone from white to an angry red.
He cast Incendio. The fire hit the ice door and vanished. No melting, no steam, and no hiss of contact. He poured more power into a second attempt, sustaining the flame, pushing heat against the surface until his wand arm ached with the effort. The fire washed over the ice and disappeared into it as though the door were drinking.
Something moved behind the ice.
Rowan stepped back. Through the blue-white surface, blurred and enormous, a shape was forming. It resolved slowly, like something rising from deep water. Armour. A helm. A sword that coalesced from the ice itself, edges forming as Rowan watched, sharp and deliberate.
The Ice Knight stepped through the door.
It was eight feet tall. The armour was ice, every piece of it, plate and chain and gauntlet rendered in a substance that looked like frozen steel but moved with the fluidity of something alive. The helm had no visor. Behind it, where a face should have been, there was only a blue-white glow that pulsed in slow rhythm, like breathing.
It raised the sword.
Rowan threw a Protego between them. The sword came down and the shield shattered on contact, the pieces dissolving into frost that hung in the air. The force knocked Rowan back a step and the cold from the impact ran up his wand arm into his shoulder.
He fired a Confringo at the Knight's chest. The explosion detonated against the armour and the ice absorbed it. The blast, the heat, the concussive force, all of it drained into the Knight's body and the glow behind the helm pulsed brighter.
It was feeding.