Harry hissed and took a breath.

This familiar feeling.

It is even more "heart-wrenching" as magic energy fills the body.

This is the "Thunder Potion".

In stormy weather, you can increase your strength and agility. Of course, the new potion brewed with the new recipe seems to have the effect of enhancing magic power.

It was a pity that today was not a thunderstorm day, so he could not test the potion's effect. He could use a weather spell, but Harry was not proficient in it. He could only create a simple breeze or drizzle, but was still a little short of summoning a thunderstorm.

Harry bottled the potion in the cauldron into three bottles.

He took out the parchment again and calculated the cost.

Even without counting the losses from previous experiments, just these three bottles of potion would cost more than two hundred Galleons—the venom of the eight-eyed giant spider was hunted by himself in the Forbidden Forest, otherwise the cost would have been even higher.

Harry sighed.

Fortunately, he had a good godfather and some savings, as a bottle of potion was really expensive.

This is just the first bottle.

A witcher can't have just one potion.

In less than a week, Harry had created the second potion - "Killer Whale". Its original effect was to effectively increase lung capacity, but after Harry's research, he used a series of materials such as mermaid blood and gillweed to greatly improve its effect.

He had tried it himself and found that the effect of the potion could last for three hours, allowing him to breathe underwater without growing ugly gills. It could even allow him to move underwater as if he were on the ground without being blocked by water.

In the Black Lake, he really experienced the feeling of flying freely without any external force.

But after the suicide of the human whale, Harry's research and development of potions fell into trouble.

He had never been able to make his favorite blizzard. He couldn't even find many magical materials that could match this potion, which required further enhancing the senses.

The recovery potions of the Full Moon, Owl, and Swallow series are also somewhat difficult to make. The materials are all there: the voluntary blood of the unicorn, the juice of the Hokklap, and the tears of the phoenix. However, the blood of the unicorn is too pure and can purify almost all poisons.

It is difficult to have such a domineering effect as the "Thunder" potion.

And it's very expensive.

Phoenix tears were in short supply, and Harry had already used up half of the bottle Dumbledore had given him, and was trying to figure out how to get another batch.

By the way, can the tears shed by beating the Phoenix heal wounds?

The blood donated voluntarily by unicorns is even more rare, with one ounce of blood costing two hundred Galleons. But even at such an expensive price, it is still the best-selling product. Once word gets out about the arrival of unicorn blood, the entire Knockturn Alley will be packed with people.

Sirius even had a fight with Snape for this bottle of blood. He was beaten black and blue. It was not until Snape mocked him that Sirius said he bought it for Harry and only then did he take the small bottle.

It made him angry.

That evening, I told Professor Flitwick that I would take extra lessons with Harry during the summer vacation.

Wednesday, before Defense Against the Dark Arts class.

Ron was holding a picture of the moon phases: "It's a full moon again these days, could it be Professor Snape again?"

Hermione frowned, feeling a little conflicted.

She also didn't like Professor Snape's teaching style. She could hear half of the class filled with swearing, and most of it would be about werewolves. But on the other hand, who knew if another professor would be able to teach at the same level as Lupin and Snape.

"Actually, Professor Snape is pretty good too." Ron turned around, reached into the book floating behind him, and took out two pieces of parchment. "I've finished writing the paper."

Harry paused and slowed down his tone: "Ron, I may have to tell you some bad news."

Ron's heart skipped a beat: "Professor Snape won't come?"

Harry nodded.

"Why!" Ron clenched his paper.

"Polyjuice Potion." Harry spat out a potion name that they were all familiar with.

Ron swallowed. "So Sirius is coming?"

Harry nodded again.

"It's not that I don't trust Sirius." Hermione was even more confused, "But can he take classes well?"

"During the Christmas holidays, you saw that he was more comfortable in the Forbidden Forest than I was." Harry continued softly, "Believe him, in terms of magical level, he is at least an excellent wizard."

As they talked, they walked to the classroom door.

Harry pushed the door open and they walked in.

"Lupin" was already standing on the podium.

Unlike the past, he was wearing a clean but plain lavender robe without any patterns, and his hair was simply groomed and combed hastily, and that was the only change.

But Ron couldn't take his eyes off: "Oh my God, Professor Lupin?"

As soon as they sat down, he leaned his head close to Harry and whispered, "Is that Professor Lupin? Could Sirius have become the wrong person? How could he be so handsome?"

"It looks the same," Harry reminded him.

"It's his temperament that has changed." Hermione reminded.

"It was just a change of robes." Ron still found it incredible.

Harry spread the book and ignored "Lupin" who winked at him: "Don't you think Sirius is actually very handsome?"

Ron shook his head subconsciously.

"Think carefully and don't be influenced by his brain." Harry emphasized.

Ron frowned, trying to forget the embarrassing images of Sirius turning into a dog and bullying Crookshanks together with him, being chased by centaurs in the Forbidden Forest, being choked in the Black Lake, and being hit in the face by fireworks from George and Fred.

I only remember his appearance and figure.

"Huh?" Ron was surprised, "He's actually really handsome."

"He is Harry's godfather after all." Hermione said earnestly.

Harry shook his head: "Godfather and godson are not related by blood."

Ron pecked the rice and nodded.

Hermione said "Oh" and her ears turned slightly red.

Not only Ron, but also the little witches who entered the classroom could not help but look at Lupin several more times. Lupin's face was actually very good, but he was used to shrinking, and he was wearing tattered robes and had a pale face, so it was difficult for anyone to notice his appearance.

Now that he's wearing new robes and looks more or less like a normal person, and with Sirius's intimidating aura...

It is no exaggeration to say that it is a revolutionary change.

Hermione's worries did not come true. Sirius was very talented in teaching, or rather, he did not regard teaching as a task. Instead, he played with a group of children like a big child and taught them how to deal with swamp diggers.

At first, I was able to be patient and follow the instructions in the textbook on how to distinguish the camouflage of ordinary driftwood and swamp diggers.

Halfway through the class, his patience was exhausted.

I taught a very simple method, which was to use the "Thunder Explosion" when in doubt. Just blow up all the driftwood you saw, and you would be safe from the trouble of being attacked by swamp diggers.

This was very much approved by Simo.

The little badgers were a little confused. This was somewhat different from Professor Lupin's usual teaching style, but it seemed that this was okay?

Wait until the lecture is over.

"Professor Lupin" packed up his teaching materials earlier than the little wizards and waited for the get out of class to end.

Hermione raised her hands helplessly: "Professor Lupin, you haven't assigned any homework yet."

The little lions glared at her, but as soon as they looked over, not to mention Harry next to them, they didn't have enough courage to look the "lioness" in the eye, and they immediately looked away.

"Oh, yes, homework." Professor "Lupin" slapped the desk and suddenly realized.

Hermione and Harry couldn't bear to watch.

The familiar feeling is back.

"Well, forget it." He waved his hand, "Compared to boring homework, it's still..."

Harry coughed twice.

"Practice is more interesting." Professor Lupin immediately changed his tone and said seriously, "So, write a paper on how to identify swamp diggers and deal with them properly instead of using an explosive spell to solve the problem. Submit it next Monday, three inches."

The little lions burst into cheers.

Professor Lupin is really different today. The paper is only three inches long.

The little badgers were a little dumbfounded.

The three-inch paper is really good and can be written in about half an hour.

But...dear Professor Lupin.

Did you teach the things you mentioned in class?

You only taught me how to use the explosion spell to solve these things!

Hermione sighed, "Harry, it looks like we'll have to prepare different papers."

She paused and looked at Ron: "You too."

Ron nodded approvingly.

It is foreseeable that the little lions will be overwhelmed when writing their papers on weekends, and will have to ask their papers to be published and used for reference.

Thursday.

When the last Potions class in the morning ended, Harry and his friends were packing up and preparing to leave.

Snape said in his gloomy tone, drawling out his words: "Mr. Potter, I think you may have to stay for a while."

The other little wizards quickened their pace in packing their things, and some even waved their wands and cast a levitation spell to take all the things away, and then continued packing outside the classroom.

Hermione and Ron didn't move, just stood beside Harry.

"Miss Granger." Snape looked at Hermione, not even paying attention to Ron beside him, "I think I have made it clear. I just need Mr. Potter to stay."

Obviously, these words were not directed at him, but Ron still couldn't help it. He retracted his neck, his feet slipped, and subconsciously wanted to walk out with his schoolbag rolled up.

"Harry and I are going to the library together later." Hermione met his eyes and said firmly, "I think it's okay for me to stay a little longer."

Snape looked away: "Mr. Potter, I think you may have to give me an explanation."

"Professor, what explanation do you need?" Harry said in a cold tone, "If your eyes are still acceptable, I have delivered every assignment on time."

"If your brain wasn't soaked in alcohol, you would know what I'm talking about!" Snape narrowed his eyes and his tone became dangerous. He slammed the table heavily, "Black bought you a lot of potion materials!"

"He really dotes on you."

"The willing blood of a unicorn, the blood and feathers of a thunderbird, the heart of a dragon."

Having said this, he paused for a moment, gnashed his teeth, and spat out some more materials: "There is even the venom of the Loba worm, the eggs of the fire ash snake, and the horn fluid of the poisonous horned beast..."

"What do you want to do? Potter!"