"...?!"
No way, did something this thrilling happen last semester?
Without having heard William mention this, Lupin's eyes widened instantly. The sheer volume of information packed into this sentence was overwhelming. What is a soulbound notebook? What does Weasley have to do with it? And what does your magic aura refer to? Dream magic, possession of Harry... And who gifted the Soul Artifact?
Lupin opened his mouth, a flood of questions surged to his lips, but he didn't know where to start...
"Oh, it seems I never mentioned..."
From Lupin's bewildered expression, William already had his answer. William sighed helplessly, realizing that explaining these matters would be rather troublesome. Yet, seeing the curiosity in Lupin's eyes, he knew he would still need to offer some explanation... So, he sighed again, "Ask whatever you want."
...
...
"...I see."
To avoid rambling on, William used the simplest language possible to help Lupin understand what happened last semester at Hogwarts Castle. Lupin's face showed a look of realization—
"So, in Austria, the ones who killed those poachers were actually the Basilisk I had on me, transformed in advance?"
"Yes, care to say hello?"
William reached into his chest pocket and pulled out a cold "rope." He actually always kept the Basilisk on himself, as using such a magical creature as a "combat Pokémon" is incredibly useful. It can petrify from a distance, strike with poison fangs close up, and even revert to its original size to act as a meat shield.
Back then, it was thanks to the Basilisk that Lupin escaped from the pile of Quintapeds, but its appearance was so fleeting that Lupin didn't recognize it.
"It's called Poisonous Snake Green Pepper, feel it, it's nice to touch, want to try?"
Handing the sleeping little Basilisk to Lupin, William introduced the name he'd given it.
"No, thanks."
Without even a moment's hesitation, Lupin instinctively took two steps back—there's no way he wouldn't understand that Basilisks are dark arts creatures, he just hadn't realized it before. Now, looking at the Basilisk's eyes covered by goggles, cold sweat began to drip down his spine.
There had actually been such a creature on him once.
Hiss—
Never had he been so close to death from the start.
"Alright, fine, let's not."
As the little Basilisk, looking like a coiled rope now, was returned to William's shoulder, William shifted the topic back to the beginning, about the issue with Harry's mind. "Based on my tests, when Harry is directly touched by a Dementor, or has intense emotional fluctuations, his charms get an enhancement—"
"Enhancement?"
"Yes, the power of curses and evil curses seems to increase, probably due to some connection with him consuming Little Tom's soul."
Little Tom...
At first, Lupin didn't quite catch on that this was a reference to Voldemort. He hesitated for a moment, his eyes filled with some doubt, "So, is that a good thing?"
"Of course not. The primary issue is that Harry can't control this power at all. Uncontrolled power only becomes a burden."
William shook his head, explaining that it took him nearly a school year to fully control the boost that ancient magic provided to his charms, and another year to create emotion magic, because he had coincidentally encountered ancient magic when he first encountered magic, so he had no hurdles learning it from that point on.
Harry's situation was similar yet somewhat different.
He could see that when casting those enhanced spells, Harry seemed to enter a kind of unconscious state, brief but definitely present, especially since that one night, Harry endured about a dozen Dementor face-offs, almost becoming immune to them.
Losing consciousness while casting magic is a significant problem, and it's the reason William quickly connected this issue with a soul link.
"Alright..."
"Also, this enhancement is peculiar, especially concerning Dementors. You might remember during that train ride, after a Dementor consumed Harry's spell, it vanished for a moment, and when it reappeared, it seemed to have strengthened by nearly half, and he managed to cast another spell when caught again—"
The perfect demonstration of weakening and strengthening on a Dementor is by looking at the size of their cloak. The overwhelming aura that came with their reappearance left a substantial impression on Lupin. Hearing William's explanation, he couldn't help but nod.
Soon, his mind began to process rapidly, quickly anticipating what William was going to say next—
"So, you believe that if Harry gets caught by a Dementor, it could lead to a continuous cycle, perpetually enhancing that Dementor?"
"Yes, currently, I don't know if there's a limit to how much a Dementor can be strengthened, so I'm a bit scared that one day a Dementor King might appear outside the castle, one that could absorb half the castle in a breath—"
"...Can't be, right?"
"We must make bold assumptions, in the magic world, anything is possible—did you ever imagine a Niffler writing a thesis before encountering Kabuda?"
"...I understand."
"So, Harry must learn the Patronus Charm as soon as possible, so he isn't as passive when facing Dementors. I conveniently have all the 'tools' here for training—also, you should practice the Patronus more as well. The area around Hogwarts hasn't been peaceful lately, and your incomplete Patronus might not be sufficient."