J. Rowling - Harry Potter and the Prisoner of Azkaban

Neville went scarlet. Harry glared at Snape; it was bad enough that he bullied Neville in his own classes, let alone doing it in front of other teachers.

Professor Lupin had raised his eyebrows.

“I was hoping that Neville would assist me with the first stage of the operation,” he said, “and I am sure he will perform it admirably.”

Neville’s face went, if possible, even redder. Snape’s lip curled, but he left, shutting the door with a snap.

“Now, then,” said Professor Lupin, beckoning the class toward the end of the room, where there was nothing but an old wardrobe where the teachers kept their spare robes. As Professor Lupin went to stand next to it, the wardrobe gave a sudden wobble, banging off the wall.

“Nothing to worry about,” said Professor Lupin calmly because a few people had jumped backward in alarm. “There’s a Boggart in there.”

Most people seemed to feel that this was something to worry about. Neville gave Professor Lupin a look of pure terror, and Seamus Finnigan eyed the now rattling doorknob apprehensively.

“Boggarts like dark, enclosed spaces,” said Professor Lupin. “Wardrobes, the gap beneath beds, the cupboards under sinks—I’ve even met one that had lodged itself in a grandfather clock. This one moved in yesterday afternoon, and I asked the headmaster if the staff would leave it to give my third years some practice.

“So, the first question we must ask ourselves is, what is a Boggart?”

Hermione put up her hand.

“It’s a shape shifter,” she said. “It can take the shape of whatever it thinks will frighten us most.”

“Couldn’t have put it better myself,” said Professor Lupin, and Hermione glowed. “So the Boggart sitting in the darkness within has not yet assumed a form. He does not yet know what will frighten the person on the other side of the door. Nobody knows what a Boggart looks like when he is alone, but when I let him out, he will immediately become whatever each of us most fears.

“This means,” said Professor Lupin, choosing to ignore Neville’s ‘mall sputter of terror, “that we have a huge advantage over the Boggart before we begin. Have you spotted it, Harry?”

Trying to answer a question with Hermione next to him, bobbing up and down on the balls of her feet with her hand in the air, was very off putting, but Harry had a go.

“Er—because there are so many of us, it won’t know what shape it should be?”

“Precisely,” said Professor Lupin, and Hermione put her hand down, looking a little disappointed. “It’s always best to have company when you’re dealing with a Boggart. He becomes confused. Which should he become, a headless corpse or a flesh eating slug? I once saw a Boggart make that very mistake—tried to frighten two people at once and turned himself into half a slug. Not remotely frightening.

“The charm that repels a Boggart is simple, yet it requires force of mind. You see, the thing that really finishes a Boggart is laughter. What you need to do is force it to assume a shape that you find amusing.

“We will practice the charm without wands first. After me, please… Riddikulus!”

“Riddikulus!” said the class together.

“Good,” said Professor Lupin. “Very good. But that was the easy part, I’m afraid. You see, the word alone is not enough. And this is where you come in, Neville.”

The wardrobe shook again, though not as much as Neville, who walked forward as though he were heading for the gallows.

“Right, Neville,” said Professor Lupin. “First things first: what would you say is the thing that frightens you most in the world?”

Neville’s lips moved, but no noise came out.

“—didn’t catch that, Neville, sorry,” said Professor Lupin cheerfully.

Neville looked around rather wildly, as though begging someone to help him, then said, in barely more than a whisper, “Professor Snape.”

Nearly everyone laughed. Even Neville grinned apologetically. Professor Lupin, however, looked thoughtful.

“Professor Snape… hmmm… Neville, I believe you live with your grandmother?”

“Er—yes,” said Neville nervously. “But—I don’t want the Boggart to turn into her either.”

“No, no, you misunderstand me,” said Professor Lupin, now smiling. “I wonder, could you tell us what sort of clothes your grandmother usually wears?”

Neville looked startled, but said, “Well… always the same hat. A tall one with a stuffed vulture on top. And a long dress… green, normally… and sometimes a fox fur scarf.”

“And a handbag?” prompted Professor Lupin.

“A big red one,” said Neville.

“Right then,” said Professor Lupin. “Can you picture those clothes very clearly, Neville? Can you see them in your mind’s eye?”

“Yes,” said Neville uncertainty, plainly wondering what was coming next.

“When the Boggart bursts out of this wardrobe, Neville, and sees You, it will assume the form of Professor Snape,” said Lupin. “And you will raise your wand—thus—and cry ‘Riddikulus’—and concentrate hard on your grandmother’s clothes. If all goes well, Professor Boggart Snape will be forced into that vulture topped hat, and that green dress, with that big red handbag.”

There was a great shout of laughter. The wardrobe wobbled more violently.

“If Neville is successful, the Boggart is likely to shift his attention to each of us in turn,” said Professor Lupin. “I would like all of you to take a moment now to think of the thing that scares you most, and imagine how you might force it to look comical…”

The room went quiet. Harry thought… What scared him most in the world?

His first thought was Lord Voldemort—a Voldemort returned to full strength. But before he had even started to plan a possible counterattack on a Boggart Voldemort, a horrible image came floating to the surface of his mind…

A rotting, glistening hand, slithering back beneath a black cloak… a long, rattling breath from an unseen mouth… then a cold so penetrating it felt like drowning…

Harry shivered, then looked around, hoping no one had noticed. Many people had their eyes shut tight. Ron was muttering to himself, “Take its legs off!” Harry was sure he knew what that was about. Ron’s greatest fear was spiders.

“Everyone ready?” said Professor Lupin.

Harry felt a lurch of fear. He wasn’t ready. How could you make a Dementor less frightening? But he didn’t want to ask for more time; everyone else was nodding and rolling up their sleeves.

“Neville, we’re going to back away,” said Professor Lupin. “Let you have a clear field, all right? I’ll call the next person forward… Everyone back, now, so Neville can get a clear shot—”

They all retreated, backed against the walls, leaving Neville alone beside the wardrobe. He looked pale and frightened, but he had pushed up the sleeves of his robes and was holding his wand ready.

“On the count of three, Neville,” said Professor Lupin, who was pointing his own wand at the handle of the wardrobe. “One—two—three— now!”

A jet of sparks shot from the end of Professor Lupin’s wand and hit the doorknob. The wardrobe burst open. Hook nosed and menacing, Professor Snape stepped out, his eyes flashing at Neville.

Neville backed away, his wand up, mouthing wordlessly. Snape was bearing down upon him, reaching inside his robes.

“R-r-riddikulus!” squeaked Neville.

There was a noise like a whip crack. Snape stumbled; he was wearing a long, lace trimmed dress and a towering hat topped with a moth eaten vulture, and he was swinging a huge crimson handbag.

There was a roar of laughter; the Boggart paused, confused, and Professor Lupin shouted, “Parvati! Forward!”