A/N: This is an AU fic, obviously. I have altered some character's ages, in order to make everyone able to fit in properly. I also lay no claim to any of the characters here. So no suing. Constructive criticism is much appreciated, as these fandoms don't exactly mesh perfectly of anything. Tell me how you think I did at combining the two. And any information as to the last names of the characters would be wonderful. Thank you! :A/N

The Entrance Hall

The train pulled to a stop, and the students began to file out. One of the last figures to emerge was a small, slight first year, with his deep hood pulled far over his bald crown. He looked around, and hurried in the direction of the giant man, who was bellowing over the noise of the students.

"Firs' years, over here. Firs' years!"

Stepping lightly, he hoped into one of the boats waiting in the dark lake, as the boat bobbed under his weight. He stumbled into one of his boat-mates, who jumped, but didn't turn.

"Watch it!"

"Sorry." He sat down quickly, to avoid doing any more harm. There was no answer from the girl he had bumped, so he took his apology as accepted, and turned to watch the large stone castle that would be his home for the next year.

"Hogwarts," he whispered, and bent even deeper into his new black robes. The wind wrapped around him, causing him to shiver. Listening to the water splash in the boat in front of them, his boat pulled into the castle in silence.

The silence turned to whispers as the first years were herded into a small room, and left alone to wait. Nerves ran high, and there was more than a hint of hysteria in a few of the louder voices.

"How do they sort us, again?"

"Dunno. Heard it's tough."

"My brother says it's really embarrassing!"

"Your brother's a liar!"

"He's the liar," said the girl beside him. He turned, and got a good look at the girl for the first time. She was even shorter than he was, which was saying something. Her short black hair was tied in a knot at the top of her head, revealing pale white eyes and a bored frown.

"Oh." He shuffled. "How do you know?"

Sighing, she turned so that she was almost facing him, though her eyes were still staring blankly ahead. "I can just tell."

There was an awkward silence. "Well, do you know how they do the sorting?"

She opened her mouth just as the door opened. The newcomer cleared her throat, and the blind girl shut her mouth.

"Welcome, first years. I am Professor McGonagall, and this is how things will be proceeding today." She looked strict enough that not even a blind person would dare cross her. Meaning no offence to the girl standing beside him, of course. "When we go out into the hall, you will all line up. As I call your name, you will step forward, and try on the Sorting Hat. The Sorting Hat will then decide which House you will belong to. Any questions?"

Nodding her head at the silence that followed, she turned and headed out the way she had come. With whispers to mark their passing, the first years all fell into place behind her.

"Told you he was lying," was the last thing the blind girl said, before walking away. He marvelled at how she maneuvered so well without a cane or even a seeing-eye creature. Impressive.

Catching the tail end of the line, he pulled his hood down even tighter around his ears. He really needn't have bothered. There was enough dust kicked up by another arrival that he remained unnoticed.

"The Boy Who Lived."

"Yeah, right over there."

Fingers pointed, heads turned, and he felt sorry for whomever of these boys was The Harry Potter. It was a lot of attention. Poor kid.

McGonagall stopped their line in front of a high chair, on which perched a tall, raggedy hat that looked about to fall to pieces. Clearing her throat, she pulled a long roll of parchment from her robes, and called out the first name.

"Abbott, Hannah!"

A thin, trembling slip of a girl tottered up to the stool, climbing up onto it, and letting the hat fall over her face. Neither the hat nor her twitched for a long moment, before a long rip peeled away from the brim, and shouted her destiny.

"Water!"

The long table to the far left erupted in cheers, as the deep blue banner above it swayed.

"BeiFong, Toph!"

The blind girl stepped out of line, freezing for a moment until McGonagall subtely cleared her throat. Toph caught the hint, and began to make her way towards McGonagall. Another cough had her stop before she ran right into the stool.

BeiFong was a big, well known name, and it surprised him to hear it. He hadn't known that the richest Earth wizards in the world had a daughter. Though it was pretty obvious what house she would be sorted to. No sooner had the hat touched her head when it shouted out 'Earth!' to the waiting Great Hall. An older student met Toph at the stairs, but the girl shook off the helping hand, instead making her own slow way down to the cheering table on the right.

He drifted in and out of the next few sortees, as calls of 'Fire!' 'Earth!' and 'Water!' echoed through the air. His eyes were fixed on the empty table on the far right. No one sat there, and the yellow banner that hung above it was limp with the weight of it's own dust. No one had sat at that table for almost a hundred years. And by the way that people's eyes skimmed over it when they looked around the hall (he knew. He could tell), it seemed that everyone had all but forgotten that there had once been a fourth house. One that stood just as strong as the others. Before the Sorting Hat had stopped sending people there, and it's last warriors and students had faded away.

It was the last house. The dead house that had once been home to the pupils of Air.

The boy fiddled with his fingers, and waited for his name to be called.

Sokka was watching his sister fidget. She looked so small, standing up there with the rest of the first years. She didn't have anything to be nervous about. She'd been showing signs of water bending since she was little. He didn't know where she got it- he'd be lucky to make the water budge.

Katara's name was finally called, and she almost stumbled as she was grabbing the hat. Hopping up onto the stool, she jammed the hat on her head, and waited.

Her brother waited with her, watching her breath catch and her head nod ever so slightly. The rip on the hat opened, and her shoulders relaxed.

"Water!"

Sokka clapped harder than anyone else at his table, letting out a whoop for good measure. Katara's face went red as she took off the hat, placing it back on the stool before running over to the Water table. Sokka made space for her beside him, and she collapsed on the bench, grinning stupidly.

"Well done, sis." He grinned at her. "See, that wasn't too bad."

She rolled her eyes at him. "You shush. My heart's still pounding."

Sokka snickered at his sister's nerves, glad that she wasn't here last year to see him almost faint during his own sorting. Most people had forgotten about it anyway.

Turning his head, he saw a very pretty girl at the Earth table snicker in his direction, and his face heated. Most. Not all.

"Potter, Harry!"

The whole hall fell silent. Sokka craned his neck to see the boy, and beside him he felt his sister sit up straight as well.

The Boy Who Lived didn't look all that impressive. Long, shaggy black hair. Small build. Not the kind of kid that had the power to silence a whole hall of excitable teenagers.

The whispers began to spread as the hat slipped over his eyes. A few people crossed their fingers under the table. After almost a minute, the hat twitched.

"Earth!"

Sokka's shoulders slumped, as the table on the other side of the room burst into cheers. Some of them were even taking up a chant- "We got Potter! We got Potter!"

McGonnagall would have none of that, though there was a smile on her pursed lips. Earth was her house, after all.

"Roku, Aang!"

A short boy stepped out of line and walked over to the hat. McGonagall grabbed his shoulder before he was able to put the hat on his head, though.

"You will have to take the hood off."

The boy nodded, and slowly removed his hood. There were a few short bursts of laughter at the odd symbol on his head, Sokka included, but if he had taken a glance at the head table, he might have seen how all of them stiffened. The boy took the Sorting Hat, and let it fall, covering up the large blue arrow on his bald head again.

Sokka's stomach growled, and his sister elbowed him.

"Shh!"

Now that Katara had brought it to his attention, there was something different to this boy. More than an odd tattoo. Even the hat stiffened when it came in contact with his head.

The time it took for it to chose Harry Potter's house was unusual. This was just painful. One minute, then two, then three passed. Finally, just as students began to stir and realize something was wrong, the hat opened it's wide mouth.

"Air."

And the world of Hogwarts was once again thrown harshly into balance.