"Miss Chang, let's hear your thoughts."
Singled out, Cho Chang froze momentarily, but fortunately, she quickly recalled her Head of House's teachings from earlier.
She straightened up and answered, "Professor Flitwick mentioned in Charms class that standard pronunciation, the trajectory of the wand movement, and the amplitude of the wrist flick all have a direct impact on the final effect of a spell."
"Quite right," William nodded approvingly. "These are the most basic factors, and they are the primary teaching objectives set by your professors in class—to enable you to 'use' magic."
"What else?"
Percy Weasley immediately raised his hand. Upon receiving a signal from William, he adjusted his glasses and spoke confidently, "I believe proficiency is also a key factor. A person who has just learned a spell will certainly produce a different result compared to someone who has practiced it for a long time."
"Very precise," William agreed with his opinion. "Even if your incantation and movements reach textbook standards on your first attempt, the feeling and feedback from casting it ten, a hundred, or a thousand times are entirely different."
William extended a finger and tapped the desk lightly. "Especially when you practice a spell until it forms muscle memory, or even integrates into your instincts, both its power and casting speed will see a qualitative improvement."
"This is what we call 'practice makes perfect,' and it is the watershed that separates a dueling master from an ordinary wizard."
At this point, William paused, his gaze deepening slightly.
"Next, is the strength of magical power mentioned at the beginning. This concept is actually quite easy to understand," William offered an analogy. "For example, if you ask a first-year wizard who has just enrolled to fire off ten Stunning Spells at someone in one breath without stopping."
"I can't say for sure if the person getting hit would be stunned, but that little wizard would definitely collapse on the ground first due to magical overdraft and physical exhaustion."
At this, Charlie Weasley raised his hand and posed a question: "Professor, what exactly determines the strength of a wizard's magic? Is it determined at birth?"
"Magic is a rather abstract concept, and currently, the magical world does not have a unified unit of measurement," William looked at Charlie and explained with a smile. "On this issue, you might as well use 'stamina' to understand it. Repeated spellcasting causes sweating, panting, and fatigue; these physiological reactions show the link between magic and physical ability."
"Therefore, adult wizards have a significant advantage over underage wizards in this regard, because their bodies are fully developed, and their magical 'containers' are larger."
"By the same token, among peers, those with strong physiques and abundant energy often have richer magical reserves."
As he spoke, William pointed at Charlie: "Take you for instance, Charlie. As a Quidditch player, your physical fitness is among the best in your year, which implies that your ability to sustain spellcasting is superior to others."
Hearing this, Charlie grinned, subconsciously patting his sturdy arm, the outline of which was visible even through his robes.
After saying all this, William suddenly stopped.
He picked up his teacup, took a sip, and let his gaze sweep over the thoughtful group before throwing out one last question: "Aside from technique, proficiency, and stamina, what other factors do you think can determine the power of magic?"
The group looked at each other in blank dismay.
Percy frowned as he recalled his textbooks, Charlie scratched his head, and Cho Chang bit her lip in thought. It seemed that for the moment, no one could think of anything they had missed.
Just then, a hand was raised hesitantly.
It was the second-year, Cedric Diggory.
"Professor..." Cedric's tone was uncertain, sounding somewhat tentative. "I feel like... emotions, or perhaps will, sometimes have a huge impact on magic?"
Hearing this, a look of surprise flashed through William's calm eyes for the first time.
It wasn't because of the answer itself—after all, this was a point frequently mentioned in advanced magical theory. What surprised him was that this answer came from the mouth of a second-year student, rather than the high-achieving upperclassmen.
This couldn't help but make him pay a bit more attention to Cedric.
Looking at the sunny, handsome boy before him, the more William looked, the more he felt the boy resembled his own student self in many ways: looks, temperament, personality, talent...
This added a few more degrees of appreciation to his view of Cedric.
"Completely correct, Mr. Diggory," William set down his teacup and spoke seriously. "Emotions, will—these idealistic forces—are all reflected in the practical application of magic."
"The most obvious example is Dark Magic," William's voice dropped a few octaves. "Most Dark Magic doesn't actually require high technical skill from the caster, nor does it require a massive reserve of magic."
"As long as you harbor strong enough malice, anger, or hatred in your heart, even a poor student can unleash tremendous power with a curse."
"There is also a more extreme example..."
Here, William paused, his expression turning somewhat solemn as he scanned the crowd. "This example is not mentioned in your textbooks, and mainstream publications like the Daily Prophet rarely mention it."
"It is called an 'Obscurial'."
Hearing this unfamiliar term, the faces of the group looked somewhat blank.
In the silence, Percy suddenly spoke up: "I saw a publisher in Diagon Alley called 'Obscurus Books'... is there a connection?"
No one responded to his slightly atmosphere-breaking comment.
William didn't mind Percy's interruption and explained in a low voice: "When a young wizard, during childhood, deliberately suppresses their magical abilities due to some reason—or is forced to do so after suffering severe physical or psychological abuse—the magic within them gradually becomes twisted and dark."
"This twisted product has a probability of generating a dark parasitic force called an 'Obscurus,' and the wizard harboring it is known as an 'Obscurial'."
William's voice echoed in the quiet office, adding a chill to the air out of nowhere.
"Once an Obscurus erupts, it is incredibly destructive to the surrounding environment. It can make objects levitate, shatter, or rupture without physical contact."
"In severe cases, an out-of-control Obscurus can even destroy half a city in a short period."
Seeing their eyes widen and their breath held as they focused entirely on this unheard-of secret of Dark Magic, William clapped his hands, breaking the heavy atmosphere.
"The reason this example is special is that Obscurials usually don't live past the age of ten."
"A child less than ten years old, at an age where they don't even have a wand—how much spellcasting training could they have undergone? How much stamina and magical reserve could they have?"
"Yet, this doesn't stop them from unleashing magical energy that even adult wizards find terrifying. This almost overturns our previous conclusions regarding the factors influencing magical effects."
"What does this show?" William looked at Cedric. "It shows that when emotions accumulate to the extreme, magic responds to that will, producing a qualitative change."
Looking at the students holding their breath, William smiled and reassured them, "However, as I said earlier, this is a rather extreme example, and very far removed from you. For instance, according to British official records, there hasn't been an Obscurial in over two hundred years."
"Therefore, you don't need to take it to heart. Just treat it as a case study to help understand the 'influence of emotion and will on magic'."
Then, William glanced at the clock on the wall.
"Alright, it's getting late. The banquet is about to begin."
William stood up and signaled the end of the meeting. "The issue discussed today is important. Although somewhat profound, I hope you will think it over carefully when you go back."
"It will be very inspiring for your future magical studies, especially if you wish to make breakthroughs in actual combat."
The students stood up somewhat distractedly, said their goodbyes, and filed out of the office.
However, judging by their somewhat trance-like state as they left, they were clearly still immersed in the description of the "Obscurial" they had just heard for the first time.