"Expecto Patronum!"
A large mass of white mist gushed from the tip of Harry's wand, and the "Dementor" before him shriveled up instantly, shaking its head and swaying lifelessly. After going through the necessary motions perfunctorily, it transformed into a cloud of black mist and retreated back into the drawer behind it—
"Bang—"
The sound of wood hitting wood echoed in the room, and Harry couldn't help but sigh.
Even a Boggart couldn't withstand such treatment.
Though the threat of the Dementor had disappeared, Harry hadn't ceased his practice of the Patronus Charm. As Lupin put it, mastering an additional powerful defensive spell was better than not mastering it at all. Its applications were quite extensive, as most evil curses would dissipate when they collided with a fully-formed Patronus.
However, for some reason, Harry's Patronus had never taken shape, and he was beginning to doubt whether he had any talent for it.
Moreover, under his relentless torments, the Boggart used for practice began to strike. At first, its blatant refusal to cooperate earned it a scolding from Lupin. Now, though, the Boggart had become smart. It not only emerged from the cupboard and transformed into a Dementor, brandishing and flailing—
But as soon as Harry uttered the spell, it pretended to be knocked down and slunk back to sleep.
And no matter how it was "reprimanded," it seemed to completely give up—just as long as I'm not afraid, then I'm invincible!
Even William had no solution to this. Boggarts, like Dementors, were non-existent entities and couldn't truly die. If it wasn't afraid of punishment, then perhaps it really was invincible. Unlike Dementors, which are simple-minded with a focus on consuming, and feel pain when encountering a Patronus—
"Riddikulus" could only make the Boggart uncomfortable for a moment, but now this Boggart had built up a resistance, so for Harry to train, he had to wait for it to cooperate.
Left with no choice, after confirming that the Boggart wouldn't come out today no matter how he called, Harry could only start practicing without an object—
"Expecto Pa..."
"Hey, Harry, practicing... has it gone on strike again?" Lupin pushed open the door and entered from outside.
"Yes, Professor."
Seeing Lupin walk in, Harry placed his wand down with a forlorn expression and accepted the packet of biscuits offered by the other. During the days William was away over the Christmas holiday, Lupin had been staying in the Room of Requirement, cooped up because he couldn't leave before his transformation, and avoiding the dining hall. He had taken to cooking for himself, and it seemed to become an addiction...
Perhaps he had unlocked a culinary skill tree, evolving from basic dishes like hot pots and barbeques to recently trying German and French cuisine, along with some Chinese recipes he practiced. Just this week, he's begun experimenting with baking. In the recent week's Defense Against the Dark Arts classes, anyone answering questions diligently could earn some snacks—
As a result, contrasting with the silence of the Potions Class, Defense Against the Dark Arts was bustling like a marketplace, and Harry was certain by now that no one among the students disliked Lupin.
"That truly is troublesome..."
Lupin frowned and coughed into his hand before speaking, "And your Patronus..."
"Still without form."
Harry shook his head, looking dejectedly at his wand.
"Don't be too impatient, Harry; you've already made significant progress."
Lupin hesitated for a moment before patting Harry's shoulder. He wasn't lying; Harry had one of the strongest talents among the young wizards he'd seen, given how most spells came easily to him, and Lupin had observed his performance in the Duel Club—
Yes, currently the Duel Club was also being overseen by Lupin, as ever since the post-Christmas holidays, William had vanished without a word and had yet to reappear, even though the term had begun. He had become a hands-off delegator.
If not for Dumbledore assuring him that William was fine, just secluded for some pondering, Lupin might have started posting missing-person notices.
"I understand."
Harry nodded, taking a deep breath to steady his restless heart.
Each time he faced a Dementor, even one played by a Boggart, he heard that maddening hum in his head, with agitation bubbling up alongside it, accompanied by a wave of nausea—a sensation akin to drinking the potions Snape provided.
Thus... from merely shivering with cold upon seeing Dementors before, he had graduated to feeling sick at the sight of these creatures.
Lupin knew of his "condition," and the biscuits were meant to help. Harry unwrapped and tried a piece. "I added some Ethiopian Wrinkled Fig juice; it might be a bit tart," Lupin 'belatedly' noted, watching Harry's face scrunch up.
...It wasn't belated.
Detecting the humor in Lupin's voice, Harry couldn't help but cough a couple of times, though the unpleasantness and agitation were similarly expelled through the coughs.
"Perhaps we could try some 'advanced teaching.'
Only after Harry had composed himself did Lupin finally speak, fiddling with his whiskers as if weighing the pros and cons.
"Advanced?"
Harry blinked in surprise, quickly catching on and looking startled, "Professor, are you talking about a real Dementor?"