Henry pulled up a seat at the staff table just as people started to crowd around his two sisters. He rolled his eyes but let them have their own business, choosing instead to pile on the food. Hogwarts may have had many negative things about it, but Henry really enjoyed the varieties of food choices, even if they were noticeably much thicker and greasier than the food choices in Japan.

Although, Henry mused, at least here I know what I'm eating. Foods in Japan can get weird.

He idly noticed, out of the corner of his eyes, that Severus was still trying to kill him with his eyes. Henry ignored it and ate heartily.

Suddenly, Astoria screamed. Henry groaned and got up to see what the ruckus was about. He idly noticed Severus also rising up in faint irritation, and Henry felt mild gratification.

"What is going on here?" Severus drawled out in his laconic voice.

And despite the fact that he knew he should probably be paying attention, Henry sat back down and continued to eat his food, ignoring the goings-on of the Slytherin table.

At least, until Severus pulled him out of his musings. Henry sighed and stood up.

As he made his way to the Slytherin table, his blood froze in his veins as he saw what could only be his sister cradling his other sister's face.

"I, uh," Henry tried to rationalize, "I didn't expect Slytherins to be quite this stupid, honestly. Delivering curses in the Great Hall? To other Slytherins? Really?" He scrunched his nose, clearly ignoring his sisters' screams, in favor of facing Professor Snape. "You ever consider just throwing your entire House into, like, a giant hole or something?"

"Do you not care about your family at all?" Severus exclaimed, nearly wide-eyed. Then he narrowed his eyes, examining Henry's face. "I see. You really don't."

"I like Tori, but that's it," Henry confirmed. "Neither of them are particularly important, though." He idly noticed that his sisters stopped screaming in favor of listening to him. Scratching his chin, he muttered, "It should be a really large hole. With lava."

Severus's eyes narrowed even more, and he asked, "What do you mean by that?"

"Well," Henry said, entirely apathetic to the situation, "they're both lesser females of the Greengrass family, and no matter who they choose to marry, their name will inevitably be irrevocably changed away from the Greengrass name. As the heir, I honestly can't be bothered to care about what are essentially bargaining chips in this pathetic backwards society." Then he gestured in a circular motion. "The pit's rim should just be, like, on fire or something. And the lava in the middle, of course."

"H-how can you say that?" Daphne's friend (at least, as far as Henry could tell) asked, shocked and horrified at Henry's blasé approach to the situation. Henry stared at her apathetically, and she winced. Out of the corner of his eye, he could see Daphne continuing to look despondent.

"Well," Henry drawled, "usually, when I say something, I say it with my mouth." He worked his jaw a few times, just to show that, yes, he uses his mouth to talk.

Then Snape's eyes widened in realization. "You said 'as the heir'." At Henry's nod of confirmation, he continued, "What's your opinion as their brother?"

Henry merely hummed. "Hm?"

Before Severus could repeat his question, Henry turned to the two boys he saw curse his sisters, and placed a hand on their shoulders. Ignoring their flinch, he said, "Detention! With me!" He turned to Snape and asked, "When would be a good time for a detention?"

Ignoring the boys' outraged reactions, Snape silkily replied, "I'll handle their detentions, as their Head of House-"

Henry interrupted with a wagging finger. "Ah-ah-ah! Nope! I'm gonna supervise their detentions."

Snape frowned. "I'm their Head-"

Henry interrupted again. "Yes, I know, Head of House of Slytherin," he replied, digging his ear with a finger, "but you see, I don't care. Besides, I have some untested arrays that need testing, and what better way than using these two as guinea pigs?" He finished his sentence happily, and clapped his hands over their shoulders.

The two boys gave an outraged shout, and Henry crouched down to them to be eye-level with them. "Did I stutter?" he asked in a low voice. At their head-shaking, he said, "No? Then there's no reason to be confused, is there?" The two boys shook their heads again, and Henry smiled unpleasantly. "Good."

Standing back up, Henry grinned. Clapping his hands together, he told Snape, "I've always wanted to see what happens when people get their skin turned inside out."

"That could have gone better," Henry said lightly, sitting in his chair in the Headmaster's office, surrounded by the other four Heads of House and a few other Professors Henry didn't immediately recognize. On the bright side, Umbridge wasn't here. Henry assumed she just didn't want to bother with the meeting, but she also wasn't at the dinner last night, so Henry was rather confused by her absence, before he abruptly stopped caring.

Severus snorted. "It could have done without the threats."

"Probably," Henry conceded with a grin. "Would've been less convincing, though."

Dumbledore cleared his throat. "You are aware that this is a serious matter?"

"Of course!" Henry chirped brightly. "Throwing snakes into pits of lava is always a serious matter." Then he tilted his head. "Unless the lava turns into water." Then he tilted his head the other way. "Well, even then it's a serious matter."

He abruptly stood up and pointed accusingly at Dumbledore. "You're making this whole thing very confusing!"

Dumbledore grinned, despite the serious air of the conversation. "I try my best, my boy." Then he frowns. "You can't be threatening the whole of the student body. In fact, you can't be threatening anybody; you're a teacher, and thus are supposed to set an example."

"I did set an example." Henry rolled his eyes. "Just because it wasn't a good example doesn't make it any less of an example."

"Regardless," and here Henry realized that, yes, Dumbledore knew exactly how his train of thought worked, "some of the students you've threatened are part of very politically powerful families."

Henry's mood darkened. "I'm completely aware, but for the safety and continued neutrality of the Greengrass name, I'm willing to take my chances." His eyes narrowed. "Nobody threatens my family."

Then, mood whiplash, as Henry jumped in his seat, smiling. "Great bargaining chips, my family! It really would suck if something happened to them."

Dumbledore stared at him.

The other professors also stared at him.

Snape put his head into his hands.

Henry scratched his head. "So. I have a class to prepare."

Dumbledore shook his head. "Not for much longer, when word gets out."

"All the more important I continue to do my job!" Henry smiled. "At least until I get fired by the board or something." He tilted his head. "Or that Umbridge lady? Can she fire me?"

Dumbledore nodded his head. "Yes, she can. But I suppose you're right. Very well, continue your classes. But if I hear word that you've threatened other students again," Dumbledore warned, "I'm not going to hold back in your punishments."

"Of course," Henry said with a wink. "No problem, really. I can still hand out detentions, right?"

"...so long as you're not supervising them, yes," Dumbledore conceded.

"Sweet." Henry grinned. "Hagrid's going to be busy."

"Right, so apparently I'm not allowed to knowingly kill anybody," Henry told his first class. "I can, however, give detentions. So that's nice."

The class of seventh-years turned to each other warily, as if to say, "what the hell is he talking about?" Henry ignored this.

"Right, so. Homework check. Everyone's turned it in?" At the hesitant nods, Henry grins. "Awesome. Let's talk about polar runes and their importance in stable conduits."

Without saying a word, the class opened their books. Henry approved. "Conduits, as you remember, are a part of the skeleton of shorthand runic arrays. They're also hopelessly complicated, even with the shortcuts I'm about to teach you." Henry grabbed a piece of chalk and wrote out diagrams detailing runic conduits.

"Professor," a girl piped up. Henry paused in his chalk drawing. "How would you be able to escape Dark magic with runes?"

"You're talking about the escaping arrays?" Henry turned to the girl. "You know that technically there's no such thing as Dark magic, right?"

"Huh?" the girl asked eloquently.

Henry continued drawing the conduits as he explained. "The only real feasible way you could escape the Dark Arts from your runic array is if you pile on intent-driven redirects." Adding finishing touches on the assignments on the board, he put the chalk down and turned fully to the class. "The Dark Arts, there's no real tangible difference between them and the standard Arts you learn in class, which is what Americans call 'Light magic', even though that's a thing that Americans think and thus is horribly wrong. The only difference that runes would be able to decipher is the fact that the Dark Arts traditionally lean more towards hatred-based intent, which is where the redirects come in.

"Unfortunately, there's no real 'full-stop' mechanism to stopping Dark magic, since Dark magic is still magic, but you can, at the very least, redirect magic with a certain intent. In runes, you'd have to layer on intent layers, one after the other, just to redirect the flow of Dark magic, and you'd have to be very specific, otherwise the redirect will capture remnants of magic that you probably need to have the array operational." Henry smiled. "Okay?" At the girl's nod, he continued, "Okay, so, these over here are conduits."

"Wait," another girl chimed in from the back. Henry turned to her, and she asked, "So there's no such thing as a Dark magic detecting array?"

"Well..." Henry frowned in thought. "I mean, theoretically, you could craft a shorthand rune that emulated something like it, probably using some sort of Graffing's shortcuts, but then you'd have to worry about false positives..." Henry shook his head. "No, there's no easy array you could craft, and any theoretical array that neutralized false positives while reliably detecting the intent for Dark magic would be the size of Hogwarts itself, and that's even if you take into account the shorthand we're learning now. The conduits alone would take years to craft. Although..." Henry tilted his head. "Hm. Something to think about.

"But, no, to answer your question, there's no real Dark magic detecting array. You could make one out of intent, but then it'd trigger whenever anyone thought of something negative. Like, they don't like the size of your tie, or something." Henry grinned. "I've actually deliberately made one before. Did exactly that. Poor sucker didn't speak to me for weeks."

The class tittered a bit, and Henry turned back to the board. "Anyway - conduits. Important when making shorthand runes, because they lessen the effects of cross-contact magical contamination. Experts in non-magical society observe very similar effects in computer engineering, and they call it 'cross-talk'. I find the parallels apt enough to use that from now on.

"Cross-talk can be limited by adding conduits in mathematically-precise locations; for instance, when writing a multi-layer shorthand rune, you'd find it best to write them so that none of the node points actually connect, but the ley lines you craft can be contaminated by other ley lines in the same circuit. Conduits - well, they don't outright prevent it, it's inevitable that it happens in such a precise science, but conduits lessen the effects of cross-talk by an average of 94%. In general runic arrays, this is acceptable, but when crafting miniature golems or something more advanced, it's very much not. This is where the concept of polar runes come in.

"Polar runes intentionally contaminate ley lines. They do this because they're specifically designed to be as interfering as possible. Polar runes are the absolute corruptions of runic arrays, and despite their discovery being a complete accident, as well as a major faux-pas in rune societies, they're actually surprisingly useful in shorthand arrays. This helps conduits out a lot because they draw the cross-talk from the ley lines and place them into an area around the polar runes and, importantly, away from the ley lines. Polar runes are crafted by pairing up certain pairs of runes, and intentionally drawing them in such a fashion that they...'corrupt' each other, for lack of a better word.

"Certain runes, like ehwaz and eihwaz, pair up well together, and when used improperly can become polar runes. There's been many major studies into how they work, and we can successfully guesstimate the optimal positions for both of them to be in to be like this." He drew the first rune, then drew the second rune upside down on the first rune. "This is the only polar rune we'll be using in this year, although next year you're going to learn three more. This is because polar runes are difficult and confusing. Most importantly, used improperly, you'd ruin the entire array.

"The reason you're learning both conduits and polar runes is that they're both very, very tricky to learn together, but if we can manage it, we'll get an even better understanding of the relationship between ambient magic and the runes that empower it." Henry smiled. "Any questions?"

Instantly, a flurry of hands in the air. Henry chuckled.

"We don't want you here."

Henry paused in his routine cleaning of the blackboard and turned to the speaker, a Slytherin boy with black hair. Beside him were five other Slytherin children, two female and three male, trying to look tough and instead looking really silly.

"I guess I can see why." Henry tilted his head. "It's pretty dusty, isn't it? I'll go and move classrooms, just as soon as I can talk to the Headmaster."

"You don't get it!" another child angrily shouted. "Why are you even in Hogwarts? You don't even have magic! You're utterly useless!"

Despite himself, Henry grinned.

"Well, it's not your choice, is it? Dumbledore hired me."

The black-haired boy, obviously the leader of the clique, scowled. "Father says Dumbledore is a loon, and the fact that he hired a worthless Squib proves that." The other heads nodded and Henry fought to keep from laughing at the absurdity of the synchronicity.

Instead, he shrugged, keeping his voice carefully neutral. "Okay. So what?" He let a bit of his amusement slip onto his face. "Is that supposed to matter to me?"

"Obviously!" that other boy shouted again. Before he could finish what was obviously going to be a tirade against Squibs, Henry laughed uproariously.

"I - I can't - oh my God this is - this is just - this is just silly!" Henry managed to get out between laughs. "Really? I'm getting threats by teenagers! Me! The current heir to the Greengrass line! The youngest Rune Master in several millenia! The only European magician in history! This is just ridiculous!" Henry calmed down a bit, leaning over his desk. "How is this my life?"

Catching his breath a bit, he turned to the brown-haired yelling boy. "You know, when I was your age, I'd already learned how to kill people with a flick of my wrist." He flicked his wrist, and the kids winced collectively. Henry grinned. "A year before that, I became the youngest rune specialist in the world. In history. So tell me, honestly, since it's obviously not because I'm not qualified. I am. Many times over. I've also proven to literally everyone important that I can manipulate magic enough to at least fake being a wizard, so even that much isn't a problem. So tell me."

He glared at the kids, all amusement gone from his face. "Who's been lying to you?"

"Lying?" The black-haired boy looked at his companions, who looked just as confused as he was. "What-"

"Lying. Telling you I'm useless. Saying that I'm..." Henry scrunched his face up in disgust. "worthless. Who is it?" He leaned in towards the obviously terrified group of kids. "Because once I find this person spreading disinformation about me..." He grinned suddenly, a menacing, toothy grin that had two of the kids whimper. "Well. I'll let you figure it out."

"Once my father hears about this-" the boy started, and Henry got right in his face, glaring and looking far more menacing than any of the kids had a minute ago.

"One hundred points from Slytherin. Get out of here." When the kids refused to move, he roared, "I SAID GO!" and the kids ran for their lives.

Henry headed back to his desk. He sat down, and almost immediately drooped in his chair, holding his head up with his hands. "How am I supposed to do this? The old man never mentioned what I was supposed to do. How is this my life...?"

If a student had walked past, they would have heard the unmistakable sound of sobbing. As it was, no student walked by, and Henry was grateful.