If Callidus had thought that this new, darker streak of Harry's would carry into all aspects of their life at Hogwarts, Callidus was wrong. The following day, Harry seemed to be his normal self, without any trace of true malice or cruelty in his words or actions. But then again, they didn't have a class with Lockhart that day.

Draco's homesickness was a little less sharp, and the blond had resumed his typical chattiness. Since they had spent most of August apart, Draco had wanted to contribute his own prank ideas, aside from the terror that they were planning to rain upon Lockhart's head. As the trio made their way upstairs to breakfast, Harry had mentioned his idea to create prank items, such as the friendly-bomb, that would immediately make anyone in its vicinity act friendly.

Draco's expression was perplexed "What would be funny about that?"

Harry shrugged. "I dunno. It might be useful. What if we're facing someone who's really angry? Or someone like Quirrell who was trying to kill us last year?"

"But that doesn't exactly make it a prank then, does it? More like just a self-defence item, and not necessarily an effective one at that. If we're going to make these so-called gaseous bombs, then they should really do something more. Something powerful." Draco's face lit up with an idea. "What about a bomb that makes people feel afraid? Could you imagine? We could turn those so-called courageous lions into pant-pissing cowards."

Harry looked doubtful. "Erm - that seems a bit - harsh, don't you think?"

"Or maybe, we could make a bomb that turns people's bones into a jelly." Draco's enthusiasm only seemed to be increasing. "Ha! Just imagine them wiggling about like flobberworms."

"That - erm - wouldn't that be - maybe - harmful or illegal?"

"Or a bomb that makes people spill their deepest, darkest secrets!," Draco continued. "We would have so much blackmail material! Think of how many people we could humiliate! And if it's a bomb, people wouldn't see it coming!"

"Okay, Draco, I'm pretty sure that would be illegal."

"These ideas are all still theoretical anyway," Callidus cut in. "We don't even know if potions can be administered through inhalation."

"Well then you need to get working on it!" Draco insisted.

Callidus rolled his eyes, but didn't bother to answer. They had reached the Great Hall, and it wasn't the sort of topic that he wanted to discuss in front of other students.

Most of the girls were already seated, and to Callidus's relief, they were finally discussing matters other than Lockhart. Callidus had never been so grateful to hear about who had been having summer romances with who at the breakfast table ("and can you believe that Jhanvi Bhati managed get away with dating two boys at once? They found out about one another at an Avery garden party, and in the ensuing fight, one of them got turned into a opossum while the other had their limbs replaced with asparagus. And since then, they've both been writing her the most appalling poetry, trying to win her heart. I think she tried to rejected them both but they won't leave her alone. I heard she's been having nightmares about iambic pentameter and poorly thought out metaphors.")

For the most part, Callidus tuned out the gossip, focusing on his bacon and toast instead. By the time everyone knew about a piece of information, it was often useless, although it could be interesting to learn about who was being ostracised and whose popularity was on the rise. But these were matters of power dynamics, and it was important for every Slytherin to be aware of them.

"I heard the Hufflepuffs talking about this, and who knows if they can be trusted with valid gossip, but apparently Professor Lockhart is having a bit of a spider problem," Parkinson remarked.

"Eww!" Greengrass squealed. "That's horrible! Tell me it isn't true!"

"I'd squish the spiders for him, if he was having a problem," Bulstrode declared. "Every last one."

Callidus did his best to keep his expression neutral, but inside, he was smiling. The spell he had cast at Lockhart yesterday had been effective, it seemed. All the spiders in Hogwarts should be finding themselves inexplicably drawn towards the Defence Professor. Hopefully Lockhart did not have arachnophobia (Callidus thought this rather insincerely.) The girls only had a short moment to share their dismay over Lockhart's plight before it was time to make their way to their first class.

History of Magic was exactly what they expected: mind-numbingly boring. Callidus knew that Hermione stayed awake and took notes during Professor Binns' soporific lectures, and he could not help but respect her for it. Draco was already asleep, a thin line of drool slowly pooling on the sleeve of his robes where his head rested. Harry's head kept tipping to the side, before he'd jerk himself straight up, only to have his head slowly tip back down. Callidus had chosen to focus on reading his textbook. He cared a great deal about his academic performance, but had washed his hands of any hope that he'd excel in History. The effort simply did not seem to be worth it.

The final class of the day was Potions with Professor Slughorn. With Callidus's already advanced understanding of potions, the class was, unsurprisingly, excessively easy. He used most of the class time, to jot down notes for future potions ideas that he wished to explore, or helping Harry with anything that the other boy did not understand. But Callidus had reasons for wanting to be in class this day. He wished to speak to his Head of House about continuing his independent Potions study.

Callidus was strongly motivated to learn everything he could about potions - he wanted to gain his Potions Mastery after all (and it was his goal to gain that mastery at a younger age than he had managed the first time around.) But there was another reason that Callidus wanted to be able to independently work on potions: he liked having access to his own lab. Last term, Callidus had gained an excellent source of income by using his lab to make potions for the other Slytherins. He had hoped that he would be able to continue his little enterprise this year. It was simply too lucrative of an opportunity to resist. But even without the underground potions business, he was still making money on the Poison-countermeasure Potion that he had patented the previous term.

When the class was finally over, and the students were tidying up the messes on their table and handing in their phials, Callidus informed Harry and Draco to go on ahead without him, since he needed to speak to Slughorn.

"Callidus, m'boy!" Slughorn boomed jovially, his silver walrus-like whiskers twitching above his wide smile. "How have you been? What amazing new accomplishments can we expect from you this year? Do you have another new potions in the works? A hypothesis you plan to prove or disprove? Exciting projects on the horizon?"

"That's what I wished to discuss with you today, sir," Callidus informed him, forcing his lips into a friendly smile.

Slughorn's gooseberry coloured eyes sparkled. "Oh?"

"I would like to continue the mentorship." Callidus's voice was quiet and modest, in a way that he knew would stroke Slughorn's ego. The man's desire to 'cultivate' connections and talented individuals made him far too easy to manipulate. "As I am sure you know, I wouldn't have been able to accomplish anything last year without you. Having the lab at my disposal, and being able to pursue independent projects has enabled me to get as far as I have. I was wondering -"

"I can guess exactly what it is you're wondering, m'boy," Slughorn cut in, looking immensely pleased. "And it would be my pleasure to continue mentoring such a brilliant mind as your own."

"Thank you, sir!" Callidus's smile was genuine this time. "Will you be assigning another student to oversee my activities? I believe that I am responsible and careful enough to avoid any serious mishaps in the lab, however, I will defer to your judgement in this, since you would know best."

"Ah, I trust you Callidus," Slughorn answered. "A clever boy like you would never make an elementary mistake like adding porcupine quills when the cauldron is still on the fire, would you?"

Callidus felt almost offended. "Naturally, not."

Slughorn patted Callidus's back in an overly friendly manner. "Then it seems we have come to an agreement. You may use Potions Lab Nine again. If ever you have need of me, please do come by my office on the sixth floor corridor."

"Of course, sir."

"So tell me," Slughorn's voice became conspiratorial as he leaned inwards. "What projects do you have planned this year, hm? Going to take the academic world by storm?"

"Ah, I wouldn't want to spoil the surprise sir," Callidus hedged. He might have had a lot of ideas, but having the idea wasn't the same as being near a breakthrough. While he had high hopes for himself, there was no need to get ahead of himself, or get Slughorn worked up.

Slughorn looked slightly disappointed. "Of course, of course, m'boy. I know how it is."

Eventually, Callidus managed to peel himself away from Slughorn's grip, before the old man started reliving his own glory days, or talking about his numerous acquaintances. Callidus couldn't help but think that maybe the man was a tad bit lonely, but Callidus wasn't eager to fill the role of being Slughorn's friend.

When Callidus returned to the Slytherin common room, the second-years were gathered in their usual spot. Draco was sprawled out on the sofa, his legs resting on Parkinson's lap. Harry was sitting next to her, letting her rest her head on his shoulder. Zabini and Greengrass were situated across from them, and Nott was in one of the other chairs, engrossed in a book. Davis and Bulstrode were sitting cross-legged on the floor, playing with Bulstrode's cat.

"Cal!" Harry called out. "Finished with old Sluggy? What did he say?"

Callidus let his lips quirk upwards. "He has allowed me to continue my mentorship, and has granted me access to the same lab." Callidus did not speak loudly, but his words were loud enough that most students in the vicinity would have heard if they happened to be listening. It was a way of letting everyone know that he was accepting commissions for his underground potions business.

"Awesome!" Harry replied. "Then we shall have many things to speak of later."

It took an effort for Callidus not to roll his eyes. He knew Harry was referring to their prank projects, but Harry's attempts at subtlety were anything but. Still, Callidus knew that the Slytherins would likely never betray their own to the rest of the school.

Over the summer, Callidus had already scoured the library, looking for books related to vapourizing or inhaling potions. There was a notable absence of any useful information. He only managed to find one or two historical references, mentioning that vapourizing potions was risky, and that managing dosages was unpredictable. In one case, a potioneer had even ended up nearly dying when his vapourized potion caused him to fall asleep for days, while no one checked up on him. As far as Callidus could tell, most Potions Masters of the past did not think that it was a worthwhile endeavour to pursue. But beyond just pranks, Callidus was convinced that the idea had merit.

First, he'd have to figure out the best method to vapourize potions in the first place, without letting the effects of the magic alter the effects of the potion. Then, he'd have to decide on a potion to inhale, that offered the lowest risk of dangerous overdosing. Perhaps it might be best to experiment on rats rather than himself or his friends.

That evening, in the relative privacy of their dorm, the trio gathered on Harry's bed to discuss their plans, now that Callidus had secured the lab for yet another year. None of them had learned any particularly effective privacy spells, except for one that warned them with a loud noise if anyone was trying to listen in. So, they kept their voices hushed as they spoke.

"So we're going to go ahead with this gas-bomb project?" Harry queried.

Callidus nodded. "I'm going to attempt it, at least. It really is unfortunate that there's so little literature on the subject. I suppose that if I can make headway on it, it will be advantageous to my academic reputation. Something like this might even be worth publishing in a journal, if I succeed."

"Who cares about that!" Draco interjected unhelpfully. "What matters is that we can get the prank to work."

Callidus's expression was incredulous. "Yes, because a prank is so much more important than the magical advancement of our society."

Draco did not seem to catch the sarcasm, and Callidus sighed. "As of yet, we still do not know how viable this whole idea is," Callidus continued to explain. "Having the lab helps, but a great deal of research will need to be done. I wouldn't necessarily get your hopes up too high about this."

Harry hummed. "You know, I think I know of a book that might help you."

Callidus glanced at Harry with surprise. "Oh?"

Harry huffed. "What's with that look? I read books, you know! What? I do! Actually, it was a book I found when I was looking up spells to learn for pranking. I'll find it for you in the library tomorrow. It was all about using different spells to change the state of matter - turning liquids into solids, or solids into gas, or gas into liquids - that kinda thing."

"Hm. I don't believe I've come across that particular book before. It sounds extremely helpful. Thank you Harry."

Harry grinned. "What are brothers for? Besides, we can't let you do all the work for our pranks."

"He doesn't do all the work," Draco sputtered. "We're the ones risking life and limb to actually apply the pranks."

Harry raised his eyebrows. "I don't recall my limbs ever being at risk for a prank. Or my life for that matter."

"Not with me to watch your back!" Draco defended.

Harry hummed, but then smiled knowingly. "If you say so, Draco."

A/N: I mostly likely won't post again till next week. School and writing don't mix well for me...