The Revealing Charm is a variation of the Unveiling Charm.

Its main purpose is to detect invisible units in the surroundings and make them visible.

A not-so-bright light hit the ground and began to spread around.

To Chen Yu, this 'Revealing Charm' was like the scan, eagle eye vision, or elemental sight in games; it was specifically used to detect any hidden spells nearby.

The faint light instantly swept across the entire classroom.

No changes occurred inside the classroom.

"Very good."

Chen Yu nodded in satisfaction, indicating that no one was monitoring the area.

Next.

"Scourgify!"

Chen Yu waved his wand, and the targeted area became incredibly clean.

Snape, you said I couldn't use my wand, but I'm a player, I have my pride, okay?

It's already a courtesy to attend class properly; to punish myself by not using a wand to clean is just ridiculous... This game is too hardcore. Pretending to be Little Wizards in class every day already feels odd, and then being punished by professors to clean. If I could give this game a bad review, Chen Yu might have already started raging at the developers and operators.

But Chen Yu also knew that this game was not as simple as he imagined.

The mere ability to bring game backpacks and skills into the real world was enough to drive people crazy and make them flock to it.

Perhaps this game was actually the real world of Harry Potter, just used as a background by the game system.

Snape, McGonagall, Flitwick—every professor was a master in their respective fields, and in the outside world, they would be top-tier figures.

Not to mention Dumbledore, who was called the greatest wizard in this world.

Attending Hogwarts was equivalent to studying at Harvard or Cambridge, a dream for countless people.

This was one of the real reasons why Chen Yu honestly listened to the professors and sat down diligently for class.

After checking again to make sure no one was peeking, his gaze lingered on the storage cabinet by the podium.

That was where Snape often kept his Potion Class ingredients.

Chen Yu wasn't trying to steal some Potion Class ingredients to brew his own Potion Class.

Instead, he walked to the cabinet, opened the bottom-most layer, and rummaged through a dozen old books, finding 'Advanced Potion-Making'.

At the bottom of the book's cover, Chen Yu found a line of text: "This book belongs to the Half-Blood Prince."

This was Snape's textbook from his school days, containing his youthful ideas for improving Potion Class and some spells.

"Snape seemed quite chuunibyou in his youth. Who would name themselves 'Half-Blood Prince' for no reason?"

Was he saying he had a mixed bloodline, half pure-blood, half Muggle?

Or was he hinting that he would protect Lily like a prince?

Chen Yu didn't know Snape's thoughts from his teenage years. He activated the system's camera function, quickly flipped through the pages, and took a series of "click, click" photos of the content on each page.

Chen Yu had accidentally discovered that the system interface actually had a camera function.

As long as Chen Yu opened the system interface and found the camera function button, his eyes could transform into a camera, taking pictures of what he saw and storing them in his brain, allowing him to retrieve detailed images from the depths of his mind at any time.

This was a form of photographic memory.

Chen Yu was worried that Snape might have placed some unknown defensive or detection magic on the Potion Class classroom cabinet. If he took this textbook, it would be difficult to explain if Snape found out.

Anyway, considering his personality, if he knew such magic, he would definitely add it to his diary—first, to prevent theft, and second, to avoid social embarrassment.

Sure enough, not long after Chen Yu finished flipping through 'Advanced Potion-Making', Snape suddenly burst into the classroom like a large bat.

"Mr. Chen Yu, what are you doing?"

Snape asked sharply, his voice trembling slightly as he saw the book in Chen Yu's hand.

Chen Yu held up the textbook: "As you can see, Professor, I was following your punishment to clean, and I accidentally found an old textbook in the cabinet. I noticed it had a lot of dust and was cleaning it, and the scribbles on it are quite severe..."

"Put the textbook back! This is a textbook left by a previous student in the cabinet! Students are not allowed to touch anything in the cabinet!" Snape continued sharply: "Now! Immediately, get out!"

Chen Yu obeyed Snape, putting the textbook back on the bottom shelf of the cabinet.

Sure enough, either the textbook had a restriction left by Snape, or the cabinet had a restriction left by Snape.

Snape had arrived not long after he opened the textbook.

What did this indicate? It indicated that Harry in the original story could easily obtain Snape's youthful textbook either at Snape's own behest or due to Dumbledore's meddling behind the scenes.

Thankfully, he had photographed the entire textbook, and the pictures were stored in his brain, ready to be retrieved and viewed at any time.

This was a huge gain; never mind Snape acting like an old bat.

If he had known that opening Snape's old textbook would provoke such a strong reaction from Snape, he wouldn't have cleaned the classroom with magic first.

Before Snape could discover anything, Chen Yu quickly slipped out of the Potion Class classroom.

After ordering a good amount of meat from the kitchen and putting it in his backpack, he headed straight for the Room of Requirement.

In the Room of Requirement, Chen Yu still recalled the photos of 'Advanced Potion-Making' in his mind.

The focus was on the spell from 'Advanced Potion-Making'—Sectumsempra.

Sectumsempra is a powerful Dark Arts spell developed by Snape himself.

When this spell is cast, it shows no obvious signs. The victim will have large wounds torn open on their body, and the injured parts cannot be repaired by any means, including healing magic. It is a concealed, malicious, yet very powerful and effective Dark Arts.

It has immense power, concealed casting, and causes severe injury.

The reason it wasn't listed as the fourth Unforgivable Curse was because Snape invented a counter-spell.

Only through the counter-spell 'Vulnera Sanentur' can it be healed.

Of course, it might also be because Snape did not make his invented Sectumsempra public.

Chen Yu learned Sectumsempra very quickly, especially since Snape had written down his creative process for Sectumsempra in the Potion Class textbook.

Chen Yu could perfectly replicate the thought process and ideas behind Sectumsempra, following young Snape's notes.

After learning Sectumsempra, he also learned the Levicorpus, Liberacorpus, Muffliato, and Tongue-Tying Curse, as well as a seemingly useless Toenail Growth Charm.

Levicorpus is a spell that combines control and punishment; the victim is suspended upside down in the air.

This charm is usually cast nonverbally but can also be spoken aloud. The counter-spell is 'Liberacorpus'.

The Tongue-Tying Curse is also a nasty spell that glues a person's tongue to the roof of their mouth.

In Chen Yu's view, this was a silencing skill, effective against most wizards, preventing the cursed wizard from accurately enunciating spells.

Muffliato, on the other hand, is a spell to prevent others from eavesdropping. If one plans to discuss secrets and doesn't want others to know, this spell can be used.