They weren't supposed to know about the mirror.
It had appeared a few months before Merlin had and, as a general rule, the students and professors avoided it. But Merlin couldn't stay away.
He didn't want to stay away. He'd stare into the mirror for days, if he could.
He knew the others worried—they'd worried about him since the day he'd arrived, wild and terrible with his magic—but that didn't matter. Everything that mattered to him—his friends, his family, his life—was behind the glass.
Sometimes, Merlin would turn around after hours sitting before the mirror. He'd turn, expecting to see them smiling behind him, but was always met with the sight of the grey stone wall behind him. After a while, he'd stopped turning around.
In the mirror, Gwaine smiled and laughed, and if Merlin watched long enough, he could pretend that's how Gwaine had looked that final day. He could pretend everything was fine.
He'd always been good at pretending.
Tonight, they were all there.
Arthur stood at the center of the group, because Merlin always saw Arthur, even when he didn't see the others. In the mirror, Arthur wasn't The Once and Future King. He didn't wear chainmail or Pendragon red. He didn't carry a sword. Merlin refused to remember Arthur as a knight, because all he could remember were Arthur's dying words. He didn't need the mirror to remember.
He'd heard those words in his sleep every night since that day, and Merlin would give nearly anything to forget. He'd give anything but losing the people he'd already lost.
So Merlin remembered. He remembered, he hurt, and he stared into the mirror as if it could give him what he longed for.
"You shouldn't be here, Emrys," said Rowena's low voice. Merlin refused to turn, refused to look at the dark haired witch where she hesitated near the doorway. He refused to break the illusion of his life before him.
Because he knew, as he knew many things, it was only an illusion.
Arthur smiled at him through the mirror, and Merlin forced his gaze over to where Morgana stood beside Gwen. "You remind me of her," he murmured, after a long moment of silence.
"Hm?"
"Morgana. You remind me of her. You're both…" Merlin trailed off. He could have helped her. He should have, before everything went so, so wrong. He shook his head. "You're both clever, I suppose."
"Is she the one you see?"
Merlin met Freya's gaze in the mirror. She looked happy and alive and beautiful in her purple dress, and Merlin ached. He wondered when he'd become so used to the emptiness in his chest.
"No," he said quietly, turning away at last. "I see them all."