The Prince of Sloth [DxD]

A certain Castle – somewhere in the Belphegor Domain, Underworld

"Alright then, let's begin today's class," said Rudiger, snapping Seir out of his thoughts and drawing his full attention.

"Yes, Master Rudiger," Seir replied eagerly, ready to learn.

Unlike their previous introductory lesson in the open field, today's class was held in a spacious hall within the castle. The room resembled a collegiate classroom, complete with rows of desks for students. Seir sat at one of the desks while Rudiger stood at the front, positioned next to a large greenboard.

Rudiger wrote 'Human Magic Systems' on the board in bold letters before turning to address Seir. "Today, we'll be discussing magic systems, with a specific focus on the type of magic predominantly used by humans." He paused for a moment before continuing, "Now, before we delve into the specifics, I want you to tell me what you already know about it."

Having already taught Seir for a few sessions, Rudiger had grown familiar with the boy's rhythm and habits. He knew Seir was a voracious reader and often came into lessons with some basic understanding of topics. Still, Rudiger also understood that Seir's knowledge had its limits, and he was curious to gauge just how much the boy already knew about the magic systems used by humans and various other pantheons.

"Let's see..." Seir murmured thoughtfully, pondering his explanation. "The Magic System used by humans is quite different from that of us Devils. It relies on calculations and the control of magical equations to control the energies in our body to create supernatural phenomena, rather than sheer imagination and the power to create using Demonic Energy. Essentially, to produce a specific magical phenomenon, a corresponding equation must be solved. The variables in these equations can be adjusted to modify the outcome to some extent. It's kind of like algebra and calculus human children learn… I suppose..."

"Hmm… That's quite a good answer," Rudiger nodded, clearly satisfied with Seir's explanation. He began to elaborate, "And yes, you're correct—that's exactly how the magic used by humans works. They have a set of magical equations, each with its own variables. By substituting specific values into these equations, they can achieve the desired results. For example, look here…"

Pausing briefly, Rudiger moved toward the green board. Picking up a piece of chalk, he wrote a series of cryptic symbols and words that he didn't recognize, on the board before turning back to Seir. "This here is a simple three-variable equation to generate fire."

'What language is that?' Seir wondered, staring at the so-called equation with a blank expression. 'Maybe it's some ancient language that was lost to time?'

Rudiger continued, "Now… if I generate a Magic Circle using this equation…" He extended his palm, and a small magic circle appeared.

With the Magic Circle constructed, Rudiger stepped closer to Seir and held out the magic circle for him to examine. "Now, look at the Magic Circle."

Seir squinted at the glowing design, his eyes narrowing as he focused on the intricate symbols. "Master Rudiger… these symbols here…" he asked, curiosity evident in his voice.

"Oh, they're derived from the equation I wrote on the board," Rudiger explained. "I'll go over them when I teach you how to construct a Magic Circle. For now, just focus on the circle itself."

"Okay…" Seir nodded, turning his attention back to the magic circle.

"Since this is a Fire Magic Circle, if I inject my Demonic Power into it…" Rudiger said, channeling his energy into the circle. A small flare flickered to life above his palm. Pointing at it, he continued, "A small flare appears."

After a brief pause, he added, "Now, because this magic circle is based on the simplest equation of Fire, it doesn't allow for much complexity or control. But even so, there's still something I can do…"

He paused again, then began altering one of the variable values. As he did so, the flare grew steadily larger, its light intensifying with each adjustment.

"As long as I continue increasing this value and have enough Demonic Power to supply, the flare can keep growing," Rudiger explained in a calm yet instructional tone. "However, as you can see, it has no defined shape or form. It's starting to go out of control, so I'll disperse it."

With a decisive motion, Rudiger dissipated the magic circle, Immediately, the flare vanished into thin air.

Rudiger moved back to the green board, chalk in hand, and began writing another equation filled with cryptic variables. "Now, this is a slightly more advanced fire equation," he explained, pausing briefly before adding, "It includes an additional variable, so it is a four-variable Equation of Fire"

He turned back to Seir. "If I construct a Magic Circle using this equation, then…" He formed another circle, which appeared different from the previous magic circle, and once again a flare appeared within it. As Rudiger began increasing its size, the fire remained stable, swirling in a controlled form. "This time, the fire has a definite shape and isn't running amok," he said with a satisfied tone.

"Yes," Seir nodded, observing closely, and thought to himself, 'The change in the number of variables is reflected in the magic circle, huh?'

"Now, if I add yet another variable…" Rudiger continued, maintaining the Magic Circle. Without interrupting his flow, he telekinetically controlled the chalk to write a third fire equation on the board, incorporating the fifth variable into the Magic Circle at the same time, once again changing its shape. "Watch closely," he instructed.

Instantly, the fire within the circle began to expand, moving outward. It floated upward, forming a swirling orb of flames that circled above Seir's head before flying into the distance and returning back, "Now I can control where it moves."

Rudiger didn't stop there. He added the sixth variable to the equation, causing the single orb of fire to split into two identical orbs, doubling the number. With another adjustment, he incorporated yet another variable–the seventh variable–and the fireballs began to shimmer, radiating an intense light and emitting faint waves of heat that rippled through the air.

"See how the additional variables give more properties to the magic?" Rudiger said, a subtle smile playing on his lips as he demonstrated the refined magic.

Seir nodded, absorbing the information. "Yes..."

Rudiger continued, "This is how a magical phenomenon is created through calculation and computation."

Seir thought for a moment before asking, "So, there's a different equation for each magical phenomenon?"

"That is true," Rudiger replied with a nod. "Each element has its own equation—one for fire, another for water, one for wind, for earth, for ice, for gravity, and so on." He paused, then added, "But the methods for controlling them are quite similar, and the calculations aren't vastly different either. As long as you understand the basic equations of all the different types of magic you want to use, understand how the basic physical, chemical, as well as, magical properties of those elements, and have a good grasp of calculations and computation, you'll be able to solve complex equations and create more advanced magical phenomena as well."

"I see..." Seir nodded, understanding.

"Good," said Rudiger, "This will be the focus of our next few classes—learning the equations and how to compute them." With that, he began the lecture.

.

.

.

"Honestly, I hadn't expected you to complete this part so quickly," Rudiger admitted a hint of approval in his tone. "But since we're done with it, let's move on to the actual construction of Magic Circles from these equations."

Seir nodded eagerly. "Yes!"

"Good. Let's start with the simplest Fire Equation—the one with only two variables," Rudiger said, turning to Seir. "You remember it, right?"

"Yes, I remember," Seir confirmed, his quill floating in the air as he telekinetically guided it to jot down the equation in his notebook for reference.

"Excellent." Rudiger gave a satisfied nod as he glanced at Seir's work, then turned back to the green board. Picking up a piece of chalk, he wrote the same equation down with practiced precision.

After finishing, Rudiger drew a plain circle beside the equation and called out, "Now, pay close attention."

"Uh-huh... I'm listening," Seir nodded, leaning in closely.

"The foundation of a magic circle is its geometry," Rudiger began. "This is something you cannot compromise on. A magic circle must always maintain its geometry. If the geometry collapses, the entire magic circle will either fall apart or, worse, explode. And trust me, you don't want either of those outcomes."

"Got it. Geometry is critical," Seir acknowledged, diligently jotting the note in his notebook, and while doing that suddenly, a doubt appeared in his mind, "Master Rudiger since there are multiple types of geometry to choose from, is it possible that certain types of magic work better with specific geometries, while others don't work as effectively?"

Rudiger shook his head. "There might be small differences in overall effectiveness, but they're not significant enough to worry about." After a brief pause, he continued, "Where geometry really matters is in the number of variables a magic circle needs to accommodate. For example, you can't use a four-pointed star to construct a magic circle for an equation with seven variables. The parallelogram formed at its center simply wouldn't have enough edges or vertices to hold all seven variables and the lines of operation connecting them."

"I see…" Seir nodded. "So the more variables there are, the more edges you need?"

Rudiger inclined his head. "Exactly. It's a direct one-to-one ratio. For an equation containing seven variables, you'd need a seven-pointed star (Heptagram). This creates a heptagon at the center, providing enough vertices and edges for all seven variables and their operations." Then, after a brief pause, he added, "Since the ratio is 1:1 and the simplest equations involve three variables, the simplest geometry for a magic circle is—"

"A three-pointed star forming an equilateral triangle at the center," Seir finished for him.

"Correct," Rudiger nodded. "A three-pointed star, forming an equilateral triangle at the center, is the simplest geometry that can be used in a magic circle. After all, there's no stable shape made up of just two edges. This is also why three-variable equations are the simplest ones in magic—one- or two-variable equations simply can't exist because they can't be incorporated into a magic circle without destabilizing it."

"Hmm… I see…" Seir murmured, clearly understanding.

"Next," Rudiger continued, "once you've chosen the geometry suitable for your magical equation, you'll need to place the variables and the operations between them into the magic circle. Positioning the variables isn't complicated—they go at the vertices of the resulting polygon, and the operation lines run along the edges connecting those vertices.

"For example, if you choose a Hexagram forming a Hexagon at the center, the placement would look something like this..." He proceeded to draw a magic circle with a hexagonal layout, marking the relevant positions.

"If you opt for a Pentagram forming a Pentagon at the center," he added, sketching another diagram, "the placement would look like this."

Seir nodded thoughtfully, absorbing the information. "Alright."

Rudiger moved on, saying, "The variables can be written down plainly." He carefully inscribed the three variables of the Equation of Fire into the magic circle with three-pointed star. "Like this," he explained, pausing to ensure Seir understood. "Once you've written down the variables, the next step is adding the operation between them."

He turned to Seir, his tone growing serious. "Now, this is critical, so pay close attention. Operations are not something you simply write down as they are." He paused, letting the gravity of his words sink in before continuing.

"Operations are transformed into lines and relational patterns," Rudiger explained, gesturing to the board. "These lines and patterns are then placed within the magic circle to connect the variables on both sides." He paused, turning back to the green board, and drew an arrow pointing from the operation to an empty space. With deliberate movements, he sketched a pattern and continued, "This operation here is converted into this type of pattern. Other operations will have their own distinct patterns. Remember, each operation corresponds to a unique design."

After a moment, Rudiger began connecting the variables within the magic circle using the drawn pattern. "You integrate these patterns into the magic circle like this," he demonstrated, carefully forming the connections.

Stepping back, Rudiger turned to Seir. "Now, with this, the magic circle is nearly complete," he emphasized, repeating the word for clarity. "Nearly complete—but not fully, and won't produce any magical phenomenon," Fixing his gaze on Seir, he asked, "Can you tell me why? What's still missing from the magic circle?"

Seir observed the circle closely, his eyes focusing on the empty space at its center. "The sigil at the center," he answered.

"That's correct—the sigil at the center is crucial," Rudiger affirmed. "Not only is it necessary for casting the magic from the magic circle, but it also serves as the magician's mark. This sigil declares that the circle is yours—that you are its creator. It's a point of pride for any magician. By placing your sigil here, both you and your magic gain recognition. So it's extremely important, not just for completing the circuit, but also for ensuring you receive proper credit. That's why the sigil goes at the very center," he explained, pointing to the heart of the circle.

Rudiger continued, "Some magicians use the sigil of their household or their association, while others—those who aren't tied to a household—create and use a personal sigil. The choice is yours. You can either use your personal sigil or the sigil of an organization that you become part of or can simply use the sigil of the House of Belphegor. There are no restrictions regarding that."

Turning his attention back to the green board, Rudiger began drawing a symbol at the circle's center. "In my case, I use my own sigil," he said. "This sigil is unique to me. Anyone who sees this magic circle and recognizes this sigil will immediately know that the Magic Circle was created by the magician Rudiger Rosenkreutz."

As soon as he heard this, a doubt arose in Seir's mind, prompting him to ask, "Master Rudiger, if there are no restrictions on the sigil used in a magic circle, doesn't that mean others could use my sigil? And if someone with ill intentions toward me were to use my sigil to create a magic circle and commit a prohibited act—or offend someone—wouldn't that put me at a disadvantage? They could commit a crime and leave behind evidence pointing back to me through the magic circle and my sigil."

Rudiger blinked in surprise before responding, "Oh… that's an interesting concern and not one I had expected a child to raise. But I'm glad you did." He nodded thoughtfully and shrugged. "The truth is, yes, it's possible. While most magicians wouldn't use someone else's sigil—it's a matter of personal pride and honor. However, if someone harbors malicious intentions, they could certainly exploit this method to cause trouble, and frankly… there is really no method to deal with this issue…"

"I see…" Seir murmured, pursing his lips in thought, 'So, nothing like encryption for such a thing, huh?'

Noticing Seir's expression, Rudiger wondered if he was worried about being framed for something he didn't do. "If you're concerned that someone might try to harm you by misusing your sigil," Rudiger began, "you don't need to worry. There's still a way to clarify such matters."

"Hm? There is? What method, Master Rudiger?" Seir asked, visibly surprised.

"It is the frequency of one's energy," Rudiger explained. "Whether it's Demonic Power, Light Power, Touki, Mana, or any other form of energy, each has its own frequency and wavelength. Every individual's aura is different, although those with close blood ties might have frequencies that are very similar or close in range. Still, there are distinct differences. If any traces of energy remain at a crime scene, for instance, it can be tested to determine its unique frequency and then matched… this would be enough to determine if the accused is truly the convict or not."

'Oh, so it's kind of like a genetic code that is unique to each individual, just in terms of supernatural…' Seir mused, nodding, "I see…"

Noticing that Seir appeared satisfied with the explanation, Rudiger nodded to himself before asking, "Any doubts so far?"

"No… I'm following everything," Seir replied, meanwhile thinking to himself, This is a bit like studying Organic Chemistry, where you have to draw out compound structures…

Unlike many, Seir had always enjoyed Organic Chemistry and found it fascinating, so he was able to grasp Rudiger's explanations with relative ease.

Though the computation part is more like doing calculus and algebra… but anyway…

"All right then," Rudiger said, pleased with Seir's understanding. "I'll give you an assignment. Think you can handle it?"

"Certainly," Seir nodded.

Rudiger then wrote a five-variable Fire Magic equation on the green board. "Draw a magic circle for this equation in your notebook," he instructed.

"Understood," Seir agreed, and began sketching.

First, the circle itself…

Then the geometry—since it's a five-variable equation, that means a pentagram with a pentagon at the center…

Next, place the five variables at the vertices and connect them with the operational lines…

Finally, the sigil at the center of the pentagon… 'Hmm… let's use the sigil of the House of Belphegor for now…'

Bit by bit, Seir completed each part of the magic circle. Within a few moments, he had finished. Holding up his notebook, he said, "Master Rudiger… here it is."

Rudiger inspected the magic circle Seir had crafted and nodded in approval. "Alright… that looks correct," he remarked.

.

.

.

.

Author's Note:

That's it for this Chapter. Enjoy reading it.

Be sure to drop your power stones, comments as well as reviews.

If you like the story so far, don't forget to add it to your library to not miss out on the updates.