"Cool!" Ron's eyes lit up, "Can I?"
"Why not?" Harry shrugged.
Kids at this age are the easiest to be influenced by those around them.
Under the subtle influence of Harry and Hermione, Ron also put away his nonchalant demeanor from the beginning of term.
Especially for young wizards like Ron, if you tell him to learn magic potions or transformation spells, he might not be interested — but if you talk about learning some minor evil curses, that's really motivating.
Just imagine, if you could cast a few curses on Malfoy's annoying face, how wonderful would that be.
"But it seems like we need a proper place to practice spells," Hermione said with some concern, "The Gryffindor Common Room doesn't allow magic…"
"Leave it to me." Harry said.
To avoid attracting attention, Harry chose to explore the earth cave the next day.
Ron and Hermione also had perfect reasons to stall — finding a suitable place to practice spells.
While the classmates were attending a banquet in the hall, Harry skillfully sneaked down the stairs of the Defense Against the Dark Arts classroom and found the entrance to the earth cave.
The entrance to the earth cave was like a cabinet, with four clock-like dials on the door; the hands must be aligned in the preset direction to pass through the cabinet into the earth cave.
He drew out his magic wand and manipulated the hands according to the method Sebastian had taught him.
When all four hands pointed in the right direction, the entrance door opened with a roar.
Harry stepped in, accompanied by the familiar sensation of spinning, and was transported into the earth cave.
The earth cave seemed to have been deserted for many years, at least that's what Harry thought; the entire room was covered with a thick layer of dust.
He had to use a scarf to cover his nose to avoid being choked by the dust stirred up while walking.
Actually, he could have used a cleaning spell, but Harry worried that during the cleaning process, some clues might be inadvertently erased, so he didn't use the spell.
The earth cave is called the earth cave because it is located at the bottom of the Dark Magic Defense Tower, with only a few faint rays of light escaping through the skylight above.
Harry took out his magic wand and lit all the fire pits and torches.
Then he walked slowly to the desk beside him.
The desk was covered with a thick layer of dust, and Harry had to use his wand to clear the dust to one side.
To his delight, there was a letter on the desk, the handwriting seemed to be Cassandra's.
He drew out the letter, time had eroded the writing on the paper, making it blurry.
After careful examination, Harry could finally make out what was written.
"I think Grindelwald really is mad, time is a forbidden magic, even Merlin wouldn't touch it, when she comes out of that Love's Little House with Potter, I hope you can persuade that lovestruck person above, make her understand that ancient magic isn't omnipotent either.
— C.C. Malfoy"
Harry's heart leapt.
Time magic?
Could it be... after he disappeared, Villatia was experimenting with some kind of time magic, trying to find him?
He held Cassandra's letter in his hand, his mind was reeling.
If what Cassandra said is true, then Villatia likely failed — and the consequences were severe.
That explains why this century only has the dark wizard Gellert Grindelwald, but no news of his sister.
Considering her temperament, she wouldn't ignore her family.
So it's very possible... she's trapped somewhere.
Could it be the Map Secret Room? Harry noticed Cassandra's sarcastic remark, the so-called "Love's Little House," was Cassandra's name for the Map Secret Room, because that secret room can only be freely accessed by those who inherit ancient magic.
Harry put the letter into his pocket, his resolve to obtain that item grew stronger.
Even back at the vault, his intuition told him, with the help of the item in the bundle, he could break the age limit and awaken ancient magic.
Since that belonged to the principal, Harry thought, maybe... he could talk to the principal?
With the goal clear and clues in hand, Harry temporarily set the matter aside.
He found several thick books on dueling techniques from the earth cave's collection, tucked them into a traceless stretching spell pocket, and quietly left the earth cave.
He didn't plan to return to the earth cave for a while, since there wasn't anything shady like experimenting with dark magic with Sebastian.
So, for practicing dueling, let's go to the Room of Requirement.
After returning from the earth cave, Harry went back to the Gryffindor Common Room and placed the books he brought back in front of Hermione, who was checking Ron's homework.
"Here, you're wrong here." Hermione corrected the mistakes on the homework as if she were a strict teacher.
"Oh." Ron responded obediently.
Noticing Harry's return, he quickly changed the subject.
"Harry? You're back? You found it—oh, Hermione finished checking your homework, the mistakes are marked there."
Harry looked in the direction Ron pointed and indeed saw his homework.
This was their request to Hermione the academic genius, to check their homework when she had time — but Hermione sternly refused Ron's request to copy homework with the reason 'what would you learn from that,' making Ron give up on that unrealistic idea.
"Harry only has some slip-ups in his History of Magic homework, Ronald!" Hermione snarled at Ron like a lioness, "And you, Ronald, look at your mistakes! I've told you so many times! It's leviosa, not leviosar!"
"Oh." Ron puffed his cheeks and reluctantly lowered his head.
"I found it." Harry helped Ron change the topic, "We'll go later, these are the books I found there."
"'Nineteenth-Century Dueling Outline,' 'Inoffensive Minor Curse'..." Hermione held the book, her eyes sparkling, "Oh my, Harry, I've never seen these books in the library…"
"How do you know these books aren't in the library?" Harry asked instinctively.
Hermione gave him a serious look.
Harry got the hint, don't pry into academic genius matters.
Then he watched Hermione quickly close the book upon glancing at the 'Inoffensive Minor Curse' one.
"Oh my, you call these 'Inoffensive Minor Curse'?" she growled in a low voice.