Okay. I never ever thought I'd write a crossover, let alone a Harry Potter one, yet this idea would not leave me alone. Also, I must admit it was fun to write.
Reviews would be nice?
One
He first sees the new teacher in the start of year feast, sitting between other professors, much taller than himself, and looking dreadfully out of place.
He's young, that much is obvious, and yet his hair is whiter than that of an old man. It reminds him of ashes, for some reason.
He wears an eye patch over one eye, and visible below that is the dark red line of an unhealed scar. Harry supposes he must have lost his eye recently, a sentiment echoed by his companions.
When the new teacher begins to eat, he sees that he keeps his gloves on.
Two
He's a mystery to the whole school, that new teacher. The white haired child who speaks with a voice marred by experience and age.
He smiles most of the time, but his single grey eye is lost.
Nobody knows who he is, and he insists on being called 'Allen' by all of his students. Any calls of 'Professor' go unheeded.
This new teacher is like a ghost, he decides during one of their lessons. A ghost in the way that he isn't tied down to anything, that he will fly away, vanish, if you blink.
Every time he shows up to teach a lesson it's almost a surprise.
Three
After a few months have passed, they realise that the new teacher never takes off his gloves.
He doesn't dress like a wizard, preferring a black and white coat with silver embellishments and a large elaborate cross on the breast to a wizard's usual cloak. He looks like a muggle, and a strange one at that.
It's not until years later that he realises the teacher never cast a single spell in the whole year.
Four
After Peeves actually apologises to the new teacher after having accidentally interrupted a lesson, Harry, Ron and Hermione decide to ask Nick why the ghosts seem to avoid the new teacher.
Nick only tells them one thing.
We have no interest in being exorcised.
Five
Once upon a time there was a family. They were close as any family could be, all brothers and sisters, and were ruled over by the oldest brother.
Hermione puts up her hand, and the new teacher pauses in his lesson, story, to hear what she has to say.
What does this have to do with Defence Against The Dark Arts, sir?
He just looks at her with his single eye for a long moment, and the class unconsciously shrinks back from his gaze. He's still smiling. Still smiling.
The oldest brother was named the Millennium Earl, and he, along with his brothers and sisters were the descendants of Noah.
He looks at the class, as if daring them to interrupt him again.
Nobody says a word until it is time to go.
Six
He learns the hard way to never let the new teacher in on a game of cards.
He's playing poker with a few of the other Griffindors outside, the ones raised by muggles teaching the game to those raised by magical families. Ron keeps flinching, thinking the cards are going to explode if he has a bad hand.
They don't notice the teacher until he's almost on top of them, being so intent upon their game.
Can I play?
They all jump, and look guiltily around to stare at the white headed form that stands above them. He laughs and sits himself down, grabbing the cards from Harry's unresisting fingers. He shuffles like a professional.
They all pile into the Griffindor common room an hour later, each one stripped to their underclothes.
When questioned, they mumble something vague about Professor Allen being a demon with a pack of cards.
Seven
Does anyone know what an Akuma is? No? I didn't expect you to. They were all destroyed centuries ago, now.
Eight
One day the teacher is late for class, and Harry has too wide a streak of curiosity to pass up the chance to learn some more things about the enigmatic professor.
There's a plain black book sitting on the desk, and Harry opens it to the first page, feeling the familiar thrill of adrenaline as he senses this is something he should leave well alone.
Just inside the front cover there are four lines of handwritten text, sloppily done, as if the person writing them didn't care enough to do a tidy job.
And I saw it was filled with graves,
And tombstones where flowers should be;
And priests in black gowns were walking their rounds,
And binding with briars my joys and desires.
He asks Hermione about it after.
Those are lines from a poem, The Garden Of Love by William Blake.
Harry remembers reading something about William Blake. A poet who wrote two books, The Songs Of Innocence and The Songs Of Experience. He believed the world to be divided between those two forces, innocence and experience.
It feels important, somehow, but Harry isn't quite sure how the pieces fit together anymore.
Nine
They say that, in the dead of night, music comes from the new teacher's room.
Always piano music, always breathtakingly beautiful and chillingly sad. Nobody quite knows how this information gets around, but somehow everybody knows it. A few people claim to have heard to music firsthand, while sneaking around the corridors after hours.
Being as insatiably curious as always, Harry sneaks out one night to hear for himself.
The door to professor Allen's class is open, and, true enough, music emanates from inside. He stops for a few moments, his breath caught in his throat, to listen to the haunting melody that grabs him, holds him tight. Even though it's only a song, even though it's just simple notes played on a piano, he still feels a tugging at his soul and a lump in his throat.
It's not until he gets to his room, after running the whole way back, that he realises he's still crying.
Ten
He goes back a week later, and this time he's better prepared.
This time he makes it to the door, which is, luckily for him, wide open. Inside, professor Allen sits at a white piano, playing. As Harry walks in he looks towards the door and smiles, and Harry shivers under his invisibility cloak, glad of the protection it gives him.
The professor's gloves are off, laying on top of the piano, and one of his hands is stained blood red. Blood red with fingers ending in black claws, looking more like something that should belong on a dragon or a demon than a human. As if he senses him looking, the professor pulls his gloves on, carefully sliding them over the strange, scaly skin of his hand. Harry wonders if it's a curse.
He pulls his eyepatch down, and Harry only then becomes conscious of the fact that the professor's missing eye was exposed and he never realised. He's quite glad really, as he always found missing eyes to be slightly creepy.
The new teacher gets up from his stool, and walks forward. Harry finds himself completely unable to move backwards. He wonders briefly if this is some kind of spell, a strange magic wielded by the professor.
It's a little late for you to be up, isn't it Potter?
The spell is broken and Harry runs, pursued by the sound of laughter.
Eleven
Hermione tries researching those Akuma things that the professor mentioned once, frustrated that there is something she doesn't know about.
She must have gone through about a hundred books before falling asleep on the couch in the library and waking up with the right book laying on the table in front of her. She rushes into the common room, desperate to share her newfound knowledge.
Akuma were machines, made from the souls of the dead. You remember that person he told us about once? The Millennium Earl? Well he was their creator. He'd go to those mourning the dead and offer to bring their loved one back to life. He'd then bring back that loved person as an Akuma, and the Akuma would kill the person who brought them back and wear their skin.
Ron looks disgusted, and Harry honestly can't blame him. The whole thing sounds like some sick joke, especially when she shows them a picture of the 'Earl' who just looks like a caricature of a Victorian gentleman.
For the first time ever, Harry wonders if it is wise to pry into a person's secrets.
Twelve
Professor Allen asks him to stay behind after class, and he grudgingly obliges. His friends and classmates go ahead to charms, taking with them a note that explains his absence. Ron nudges him and offers a reassuring grin before he goes. Harry tries to return it.
Professor Allen asks him to sit down, and he complies, sitting at the chair the professor set at the other side of his desk especially for that purpose.
So, you and your friends have been prying into my secrets.
It's a statement, yet Harry finds himself nodding anyway. His throat is tight from something that feels a bit like fear and a bit like reverence and he doesn't quite trust himself to speak.
Well, it's impolite to do as such, and my secrets are not the sort that can be pried.
He pauses then, and leans back in his chair. He takes a pumpkin pastie from his desk drawer and lays it in front of him. He grins and holds a second pastie to Harry. He refuses.
Well, what did you want to ask me, then? You may as well ask me to my face. Unless you don't really want to know who I am...?
Harry opens his mouth, and closes it again when no words escape. The teacher's grin widens, and Harry can't help but flinch. He's reminded of an angel and a demon, fire and ice, sanity and madness, innocence and experience. All questions dry in his mouth, and he feels the cold touch of fear at the back of his neck. He shivers despite himself, and the professor laughs. Cold, high, melodious, unlike his usual laugh. He sends him off to charms, and Harry can't help but wonder if it's a trick of the light that the teacher's skin looks so grey.
He can't quite bring himself to concentrate on classes for the rest of the day.
Thirteen
Professor Allen leaves at the end of the year, and Harry wishes he wasn't quite so glad.
Fourteen
... Unfortunately, not much is known of Exorcists from those times as most records of their existence were destroyed by the Church after the fall of the Noah. From what is recorded, we are able to tell that all those who were once Exorcists were betrayed by the Church and executed as sins against nature after the Akuma died out. A single Exorcist survived this punishment, and he was never discovered. His name is unknown, as it was scratched out on the original document. We are able to surmise he held great power.
From the book 'Magic and Sorcery of the uncertain period'.