He became a professor for the smell of chalk, for the shape of bleached lime on dark slate, for the way it flaked, and for the rivulets of white dust fluttering down against smooth, cold black. He became a professor for the unexpected art of magic, for the self-indulgence, for all the wrong reasons.
Like most things, there was no going back.
He had hated Transfiguration back then, back when he used to take charcoal to class instead of quills, because he always could have borrowed from Seamus if he'd really needed to, back when all that mattered was whether Gryffindor would win the next match or when the next Hogsmeade weekend fell.
He spent the first four years sketching and drifting away and thinking the impossible, and didn't come back to reality until fifth year came around and he realised that magic was not all tricks and deception, and he really needed to know things.
"Pincushion, Thomas," McGonagall had said, and it had shrunk away from her approach, curling tight around itself. He had looked at the patchwork hybrid, and then up at her, and she had not been impressed. "Perhaps," she had sniffed, "you should try actually learning the spell."
He had conceded that yes, perhaps he should, and had always proceeded not to do so.
It was a child's nightmare, the kind you dream when you don't know that there are worse things to be scared of. And he hadn't had it for years, not since before Hogwarts, before the world changed and folded in on itself, coming out skewed and flipped, and he realised that there was an entire other side to everything that he had missed.
His mother said, "It's nothing, it was probably you," but he knew it wasn't. It came with a prickling of dread, lacing its way tight down his spine as he slept, and a whisper of breath from invisible lips against his neck, and the ghost of a hand curving over his wrist. It made his pulse quicken, his eyes clench, his jaw work, and no sound would come, just choked and muffled gasps, until his voice tore itself from his throat, and they came running.
"It touched me," he would say, his voice thin and plaintive, and they wouldn't have any answers. Then he would sleep with his arms tucked close at his sides, buried as deep under his blankets as he could despite the stifling heat, until he forgot.
"It was your guardian angel," said his grandmother, in her strange scattered accent, but he thought it mustn't be guarding too closely, because he didn't feel it again until Hogwarts, until the Boggart.
Seventh year advanced Transfiguration was not, he discovered, all it was made out to be. Theories and diagrams and scripts, explanations and deconstructions of spells in languages he couldn't speak but had to anyway, to make bones disappear and to rearrange the energy into inanimate carbon bonds. They didn't call it carbon, and they never talked about molecular structure, and he didn't understand, but McGonagall told him he didn't need to.
Units of study like animation and shapeshifting and reconstruction and consciousness, and he passed them all, excelled at them all, hated them all, and never could Transfigure a satisfactory pincushion. It still curled up when he touched it, so he tried not to. If he ignored it maybe it would stop being true.
Seamus taught him the light spell on the train, in the two-hour purgatory between Hogwarts and the real world. "Like this," he had said, smiling his crooked smile, and the very word of the spell sounded vibrant in his voice. It had flared like lit calcium, then dulled, and went out when Seamus told it to, and Dean had never believed it before then.
"I'll show you," Seamus had said, and Dean's hand shook on his wand, unsteady and unsure. The word was awkward and heavy in his mouth, meaningless and foreign like a language he should know but didn't, and he felt the light in his blood even before he saw it.
He hadn't thought it would work, but it did.
"Have you ever considered alchemy?" McGonagall asked him once and only once, and Seamus elbowed him sharply and conspicuously, like it was his fault for knowing these things, for knowing the wrong things.
"No," Dean said, sullen and expectant, because it was just last night he'd fallen asleep with the book with paper like leaves, dead and decaying like the science itself, and she had told him to get to bed.
But all she said was, "Perhaps you should," in her sharp, tartan-print voice, and he scowled, because it was more than about turning lead to gold. It was about being the lead and accepting that no matter what, you were always going to be toxic-- only you just didn't tell people that.
Seamus woke him up next time with his fingers on Dean's palm, and it was just like the dream, only this time it was Hogwarts, and this time it was Seamus; and if angels had ever existed, they didn't anymore.
In the end he got her job because she died in the war along with the rest of them, and he lived on, and no one remembered the way things used to be. The graveyard stretched out beyond the lake, beyond the property line, and it reminded him of the playgrounds back home, before they were torn up: of goal posts and bulldog lines and swings and seesaws, things that meant everything then and nothing now. But these were rows of tombstones in alphabetical order, overgrown with grapevines without a single grape, and he kept all the names written down, every little syllable, printed on white parchment in black charcoal, because there was no one left to borrow ink from.
He dreamt three hundred and sixty-four days a year, of paisley hedgehogs and carbon and lead and guardian angels, and on the last he went out and outlined every letter in clean white chalk, soft lime against smoked limestone; he carved ghosts into tombstones that were gone in the morning.