"Today is a practical class."

Felix said standing on the podium. He waved his hand, and hundreds of wooden jars appeared in the air, floating in the air. Then he waved his hand again, and the space in the classroom began to extend in all directions, and in the blink of an eye it widened to half the size of the auditorium.

The students exchanged excited looks and whispered to each other.

Then, a large book with a simple and ancient shape appeared in Felix's hand. He opened the first page, and a tide of colorful ancient magic words poured out of the book. Each one was half an inch in size. They were like some tiny flying creatures entangled and connected together, like an unfolded long scroll, or a gorgeous long carpet - but it was not woven with thread, but made of magic words.

Felix and the students silently looked at the magic runes that surrounded them like a wall for a while, and then said:

"Some of these magic runes are special. They cannot be well integrated with the characters around them. What you have to do is to pick them out - it tests both your eyesight and your skills, because if you are not careful, it will destroy the nearby structure... Successfully picking the next one will add one point. You can use chestnut jars to store the extra magic runes. The final score is related to the length of your homework today. Let's get started."

"Oh, by the way, you can't use magic wands. This will become the criterion for future practical classes."

Students came forward one after another to choose the jars they liked, and Felix himself sat on a soft chair, recalling the academic conference that had just ended.

There were many people present, from all over the world. According to the original plan, the evening party on the first day was similar to a welcoming party, which provided opportunities for communication and meeting. This kind of thing is unavoidable, because many people's impression of each other remains on the names and academic content of academic journals, and they can't match them with real people.

Therefore, someone had to play a role similar to that of a host, and Felix's best candidate was naturally Slughorn. The old professor was like a fish in water, and the smile on his face never stopped throughout the whole evening.

Mr. and Mrs. Tonks also came.

They stopped in front of the huge booth for a long time. In fact, they didn't quite understand what these people were discussing, nor could they accurately distinguish the meaning of the magic sequence that Felix had solidified with magic in front of them, but every time they heard the exclamations of the experts, their position in their hearts was shaken.

The hall on the first floor of the Sword Castle was crowded, and they were searching for their daughter. Finally, they found her next to a wide pillar. Lupin next to her had a calm face, but was very excited in his heart. He remembered the promise that Felix had made: with the invention of the wolfsbane potion, new theories will emerge in an endless stream, and the situation of werewolves will improve.

To a certain extent, these words have indeed come true one by one. In just the past two years, an improved formula for wolfsbane potion has emerged, greatly reducing the cost; the Ministry of Magic has also passed legislation that all registered werewolves can enjoy discounts when purchasing wolfsbane potion.

As a result, a considerable number of werewolves chose to be neutral during the war.

But none of this was more exciting than what he heard earlier tonight. Lupin had learned about the two solutions proposed by Felix - ancient magic that can control the transformation of werewolves; and advanced human body transformation that transforms the internal structure of the body - he had the hope of doing both, and the latter could even allow him to temporarily become a real human, which meant that he could have an extremely healthy child.

God knows how ecstatic he was when he learned the news.

In fact, the symptoms of werewolves are not 100% inherited by offspring, but for Lupin, this is tantamount to waiting for God's judgment. He who has been tortured by the werewolf identity for decades cannot bear this uncertainty.

There was also an episode on the day of the dinner.

Lucius Malfoy and his wife appeared in a high-profile manner. The couple was dressed gorgeously and promised to donate 50,000 gold galleons generously for good causes. This attracted many people who lived abroad and were not sensitive to politics to gather around him and listen to him talk about his son Draco's "dream of being a healer".

The effect was... not bad.

"The newspaper said," Hermione carefully looked at the glowing scroll in front of her, which was like a tightly embedded brick, and said, "More than two hundred people were present. They are experts in the three fields of potions, treatment and alchemy. Officials from the Ministry of Magic of different countries were also present."

She put her right hand on the rune wall and easily took down a glowing ancient rune.

"What a big deal." Harry said in admiration.

"But the strange thing is that the host of the press conference is Professor Slughorn." Hermione said.

"Not surprising," Ron said from the side. He saw Harry also successfully take down an ancient rune and stretched out his hand towards the glittering wall eagerly. "We all know that he is good at this. Think about who can make a moving eulogy in front of a huge and hideous spider corpse? Oh, no."

He groaned and tried to put the ancient rune back, but it was too late. The dozen runes in front of him flashed dangerous red light.

"Bang!"

Ron was drowned by black smoke. He covered his mouth and coughed. Harry and Hermione quickly hid aside and almost squeezed Neville against the wall. "I'm sorry, Neville!" Harry said to Neville, who was rubbing his chin with tears in his eyes, "It's okay."

Ernie, who was standing by, didn't pay any attention to this little accident and kept talking to himself, "Justin got six points. I don't want to lose to him."

When the smoke cleared, Ron grumbled to Harry and Hermione in dissatisfaction, "You ran so fast. I almost sprayed the leaves of the mandrake. Hermione, you should have reminded me."

"You chose the right target, but your technique is wrong." Hermione pointed out his mistake, then flicked her fingers and deftly picked up a rune from the wall and waved at him.

"Like this, use your magic to stabilize the surrounding connection points. We only need to pick out those characters that look inharmonious, so it's easier."

"I know." Ron said weakly, "My attention was diverted. We shouldn't talk about Slughorn. It's better to think about it-" He paused, gritted his teeth and took off an ancient rune like pulling out a building block.

At the same time, Harry uttered a word: "Blood Pact."

Hermione took a breath, her fingers trembled, and a concrete character turned into pure magic, dispersing like smoke. "Be careful!" She shouted nervously, quickly condensing an ancient rune from her fingertips and stuffing it back. The three of them stared at the wall cautiously for a moment until the red light on it stopped flashing, and they breathed a sigh of relief.

"This game is quite exciting." Ron said impartially, he was in a much better mood.

Hermione looked around, and everyone's attention was attracted by the noise made by Cormac McLaggen. She took the opportunity to lower her voice and said, "I think it's best not to tell anyone, especially when it comes to that person." She showed an incredible expression, as if she was about to scream in the next second, but she tried her best to suppress it.

"It's incredible. I mean the headmaster and..."

Harry was silent, taking down the glowing characters from the wall. These were what he saw in the Pensieve last week. At this point, he could no longer hide it. He was deeply involved and urgently needed to find someone to discuss it. The people he trusted most in school were undoubtedly Ron and Hermione.

In the last class, Harry saw a brand new and subversive memory.

Young Albus was preparing for his graduation trip with high spirits, but tragedy struck him in the blink of an eye. His mother died unfortunately because of the magic out of control caused by Ariana, and he had to return home to take care of his younger brothers and sisters. Harry witnessed his pain and anxiety throughout the whole process, and for the first time accused Albus of being impatient. Of course, the person in the memory could not refute it, but the owner of the memory could, but Dumbledore acquiesced to everything.

This made Harry feel a little regretful. Putting himself in their shoes, if he had to continue to stay with the Dursleys after he became an adult, he would definitely go crazy. But after all, they were his relatives, weren't they? But when he saw Albus establish a friendship with a young man, Harry was happy for him from the bottom of his heart.

Until he heard that name.

"Hello, my name is Gellert Grindelwald."

Harry suddenly remembered the letter he had read. His mother Lily mentioned in the letter to Sirius that Dumbledore and Grindelwald had been close friends, but perhaps due to the length of the letter, Lily did not mention the cause and effect in the letter, let alone the time. Therefore, when Harry heard this name from the blond boy in front of him who was not much older than him, he seemed completely unprepared.

What followed was a long fragment of memory, but it was enough to make Harry realize that their friendship was progressing rapidly. He even read several passionate letters from the perspective of an observer. They appeared in front of him in a sudden and extremely uncomfortable way. Muggles, rule, government, army... These words appeared in front of him like sharp thorns, constantly stabbing his heart.

But all of this was not as good as the scene in the barn.

Two people - young people who will be famous in the future - Dumbledore and Grindelwald, facing each other, cut their palms with their wands, and then put their hands together, the blood intertwined, and the dazzling light illuminated the two young and solemn faces.

Harry felt dizzy. Finally, when the blood beads that merged together and became indistinguishable were covered with a metal shell, he loudly asked what it was. Dumbledore was speechless. He almost forced Harry to tell him in a weak but strong voice that it was the "blood oath". He and Grindelwald made a blood oath.

The class ended hastily, in the way Harry least wanted.

"Harry, Harry?" Ron shouted, "We are already behind, and I don't want my homework to be two inches longer today."

"Got it." Harry muttered, and got busy, but he had made up his mind.

Before the class ended, the students lined up to be tested.

"Susan Bones, 52, well done, homework - one foot; Anthony Goldstein, 47, one foot two inches; Millicent Bulstrode, 29, well, you need to practice more, otherwise you can't keep up with the next stage - the length of the homework is one and a half feet."

Felix commented casually, and the long line gradually decreased.

Harry deliberately stood at the back, holding the chestnut jar, waiting for Ron and Hermione to walk away, and then walked forward.

"Harry Potter, let me see - 59, ranking quite high, very good, the homework is seven inches."

Harry racked his brains and asked two questions, waiting anxiously for other students to pack up their bags and walk out of the classroom. Ron and Hermione knew what he was going to do, waved to him, and left first. Felix looked at him thoughtfully.

"It seems that your real question cannot be heard by others."

"Well, yes... Professor, I want to ask what the blood pact is?"

Felix showed a surprised expression.

He thought for a few seconds in his mind -

"There are many contracts in the wizarding world, from verbal agreements with little binding force to magical contracts. The most solemn and cautious type of contract is treated with caution. Once signed, it cannot be violated. Because the cost of breaking it is too high."

"Death?" Harry asked softly.

"...Yes, such as unbreakable vows, and of course blood covenants. It's just that the conditions of the latter are more stringent and only exist in legends." "

Why? Aren't their effects similar?" Harry asked puzzledly: "Except for the difference in the number of people, an unbreakable vow requires a witness."

"I can name many differences, such as - as you said, an unbreakable vow requires three people." Felix said, and Harry blushed. He felt that he was a little slow and didn't notice the "many differences" mentioned by the professor at all.

"But the most important thing is the content of the oath. The content of the unbreakable oath is more flexible. I can swear that I will never eat chocolate frogs in my life, or I can make myself walk through the door with my right foot from now on... In short, there are no specific requirements. But the blood alliance is different. It has its own magical core. There is no need to say the contract to be followed. This brings a very serious impact. Can you find it, Harry?"

Harry tried to think hard. No need to swear... What does this mean? No need to waste words? No, it's definitely not this... Wait, no language... No restrictions...

"The blood alliance will not be deceived by lies?" He blurted out.

Felix smiled and nodded.

"An unbreakable oath is closer to the word 'contract', so the content of the oath must be determined by words, and words... can be played with, there are always loopholes, as long as the final requirements are met. In other words, it controls your behavior and has a certain lag."

"In extreme cases, a person who is determined to die can sign any unbreakable, 'false' oath."

"But the blood covenant is not like this," Harry said excitedly: "It has fixed content, which makes it impossible to be deceived by sweet words. The two people must be absolutely sincere, even if they have the idea of ​​breaking the oath-" He looked at Felix as if to confirm.

"You guessed right, the blood covenant binds the heart, and any attempt to violate it will immediately backfire."

"What is its content?" Harry asked impatiently.

Felix hesitated.

"As far as I know, it is not to hurt each other."

"Can it be destroyed? I mean, the token formed by the blood covenant?" Harry continued to ask.

Felix glanced at him, "Did I mention the token?"

"Oh, uh-"

"Maybe it can be destroyed." Felix did not pursue the loopholes in Harry's mouth, but simply said: "I have never signed such a contract, so I don't know the specific results."

In fact, all the contracts he signed had one common feature: he could tear them up and twist them at any time. But he had no interest in touching those that he was not sure he could break, whether it was an unbreakable oath or a blood pact. What he knew was also extremely limited.

Harry left with a heavy heart.

Felix stayed where he was, watching him disappear, then suddenly raised his head and stared at the ceiling, his sight seemed to penetrate the wall. He stared at the location of the headmaster's office tower with deep thought.

Perhaps Harry himself did not realize that the direction of his question was actually very obvious.

"Blood pact... Dumbledore and who? Equally matched - yes, only Grindelwald."

Felix began to try to piece together a complete story as he continuously extracted trivial information from his memory. The first thing he thought of was the secret involving Dumbledore that Newt inadvertently mentioned and could not reveal more.