Disclaimer: I'm a software engineer, not a writer. I don't own Harry Potter.
The Most Important Spell
First year
After encountering Voldemort in the Forbidden Forest
Harry couldn't sit down. He paced up and down in front of the fire. He was still shaking. "Snape wants the stone for Voldemort... and Voldemort's waiting in the forest... and all this time we thought Snape just wanted to get rich..."
A few minutes of anxious pacing and disturbing Ron later…
When Harry pulled back his sheets, he found his invisibility cloak folded neatly underneath them. There was a note pinned to it:
Just in case.
No! Harry thought angrily, there's got to be a way I can protect myself! Maybe I should ask a Professor – Snape would probably be best if not for the whole "Potter spawn" thing, McGonagall clearly doesn't take first years seriously, Quirrel is incompetent, what about Flitwick?
Suddenly, a memory struck him, and he grinned.
Charms class, earlier that year…
"Now, don't forget that nice wrist movement we've been practicing!" squeaked Professor Flitwick, perched on top of his pile of books as usual. "Swish and flick, remember, swish and flick. And saying the magic words properly is very important, too - never forget Wizard Baruffio, who said 'f' instead of 's' and found himself on the floor with a buffalo on his chest.
Harry, dutiful student that he was, had promptly forgot about it. Now, however… buffalo summoning sounds like it could be useful, he smirked.
After defeating Quirrelmort…
Too bad I never had a chance to try summoning a buffalo, Harry thought to himself. He'd have to remember to try the next time he was attacked.
Second year
Dueling club...
Harry raised his hand. "Professor Lockhart?"
"Yes, Harry?"
"Can we use any first year spell?"
Lockhart thought over it. It'll help me get close to him, so he'll trust me more later, and there aren't really any harmful first year spells… "I don't see why not," he smiled agreeably, either not noticing or ignoring Snape's eye roll.
"Three — two — one — go!" Lockhart shouted.
Malfoy raised his wand quickly and bellowed, "Serpensortia!"
The end of his wand exploded. Harry watched, aghast, as a long black snake shot out of it, fell heavily onto the floor between them, and raised itself, ready to strike. There were screams as the crowd backed
swiftly away, clearing the floor.
…for approximately three seconds before remembering his prior resolution. Snape opened his mouth to say something, but before he had the chance, Harry swished, and he flicked, and shouted, "Wingardium Leviofa!"
To the shock and utter disbelief of nearly everyone else nearby, a buffalo appeared and crushed the snake. Remembering the spell Snape had used, Harry then casually waved his wand with a "Finite incantatem," banishing the buffalo. After Snape finited the snake, the club proceeded onwards – after all, as Lockhart eagerly pointed out, deliberate misuse of a first year spell for self-defense was in no way a violation of the rules – something Snape was quick to fix. Fortunately for Harry, with Lockhart and most of the student body defending him, he did not get in any trouble.
That night in the dorm…
Harry was having trouble sleeping. There was something he was forgetting, something important, but he couldn't remember what. Suddenly, he gasped. The snake! He was referring not to the snake which had been summoned by one Draco Malfoy, but rather, to the one he had accidentally set on his cousin, Dudley.
He wondered if there was some way he could ask the snake how it was doing – after all, the existence of a Sneakernet in no way indicated the existence of a Snakernet.
Later, during the second dueling club meeting…
"Serpensortia!" Harry shouted, using Malfoy's own attack against him (He had previously gained permission from Lockhart to do so, as long as he was careful, and Snape didn't bother showing up for the second meeting).
Harry had been thinking about the snake he had rescued from the zoo, and much to his surprise, it was that snake which he summoned!
"Hello, amigo," it hissed at him.
"Hi!" he hissed back, "would you mind scaring that blonde twit over there for me a bit?"
The snake hissed a laugh and nodded, before slithering towards Malfoy.
"Parseltongue!" Malfoy shouted, terror clear in his voice (he'd been raised on tales of Voldemort, including how Voldemort would torture his own followers).
Harry smirked, deciding Malfoy was scared enough, even if he was confused by the gibberish Malfoy was spouting. "Mind if I summon you later to talk?" Harry asked the snake.
At the snake's nod, Harry banished it.
"You're a Parselmouth!" one of the students shouted.
"A what?" Harry asked, confused.
"You can talk to snakes!" someone else yelled.
"Well, yeah," Harry agreed, "can't everyone?"
One confusing explanation later…
Huh. I guess not.
Lucky for him, his getting rid of the snake the first time, his clear ignorance on the topic, and the fact that he was very obviously not attacking anyone with the snake meant no one accused him of anything – and since he only targeted Malfoy, large parts of the student body sided with him.
Third year
Without his wand, Harry was unable to summon a buffalo to attack Black – which he later decided was probably a good thing (though Sirius had a good laugh when he learned about Harry's deliberate butchering of the Levitation Charm).
Fourth year
First task…
Summoning a buffalo to sate a dragon's hunger before asking it kindly in Parseltongue for the golden egg worked – though admittedly that was more because of his honest adoration at seeing "Oh my god! A real live dragon!" Harry exclaimed, "What a beauty!"
Second task…
"Oh well, I guess hoping they'd let the same strategy work was a bit stupid."
Fortunately, he had a better idea. First, he mugged Cedric, and stole Cedric's wand.
"Hey!" he yelled at the merfolk guarding the hostages. He held up Cedric's wand. "I'll give you this wand – you can learn Wizard's secrets – if you let the hostages go!" (He had planned on using Viktor's at first, but realized Hermione might not appreciate him doing that to her boyfriend.)
He was only mildly surprised when they agreed. And if no one ever found out what happened to Cedric's wand? Well, it wasn't like anyone asked him, now was it?
The graveyard…
"Wingardium Leviofa!" Harry immediately shouted after finding himself in a creepy graveyard. "Wingardium Leviofa, Wingardium Leviofa, Wingardium Leviofa!"
The buffaloes easily subdued Wormtail and Voldemort, and Harry and Cedric brought them both with them when they returned to Hogwarts.
Sirius was exonerated, Fudge was lauded as the champion of the downtrodden, Voldemort was handed over to the Department of Mysteries and never heard from again, and the tale of the heroic Buffalo Mage was told for millennia.
A/N: I have taken some… artistic licenses with the original text (mostly just the scene from first year – changed it to make it refer to the levitation spell – that was not a typo! Also shifted the timeline up a bit so that the Internet – and subsequently, the Sneakernet (a term used for transferring large amounts of data by physically moving a large hard drive/group of hard drives) exist.
Additionally, because of the success of the first Dueling Club, it ended up continuing for more than just one session.
One last comment: the fact that "since he only targeted Malfoy, large parts of the student body sided with him" is a valid sentence in HP fanfics just shows how screwed up canon is. Hogwarts is a frigging school not a war ground. Seriously, if I do another of these, it'll probably be Dumbledore, (a somewhat smarter) Minister Fudge, and (a more rational) Lucius Malfoy drinking together and mourning their society's seemingly inevitable downfall.
