Chapter 102: The Mana Engine

Cantrips—those basic magical tricks that fall outside the realm of formal spells—are accessible even to apprentice mages. They’re usually incredibly simple to learn, with spell models so straightforward that even a young child could grasp them. But naturally, their effects are limited and one-dimensional. Many cantrips have little practical use in combat or work, serving mostly as supplements to formal spells or as a kind of “preschool education” for budding spellcasters.

Gawain knew a few amusing cantrips himself. Take “Chromatic Hair,” a preparatory cantrip for Transmutation magic—it dyes the target’s hair a random color, but that’s all it does. It has no offensive power and lasts only two hours. Or there’s “Willpower Training,” a cantrip designed purely to strengthen mental resilience. When cast, it summons a phantom visible only to the caster, which immediately begins reciting the caster’s youthful, angst-ridden poetry—nonstop, until the caster chooses to end the effect. It’s surprisingly effective for mental fortitude…

Well, that last bit was Gawain’s own interpretation. Locally, mages say the phantom instead drones on about all the caster’s failures and foolish mistakes. Since only the caster can see it, it’s a kind of psychological suggestion—a technique straddling the line between magic and mental discipline. It’s great for self-reflection and learning from experience, but most people don’t want to bother with it.

Formal mages don’t like to call those who only know cantrips “spellcasters” like themselves. Street performers who fool ignorant commoners with a few tricks, or apprentices who bluff their way past provincial knights with cantrips, are considered inferior. Even apprentices don’t take pride in mastering just a handful of cantrips—but on the flip side, if you can’t even manage a few cantrips, that’s truly embarrassing.

Rebecca was clearly a champion in the “mage shame” category.

The repulsion cantrip that nearly gave her childhood a psychological scar was one of the few cantrips with some real power.

It’s a foundational spell in the force-field school, a variant of the cantrip “Telekinesis,” and a stepping stone toward more advanced spells like Gravity Manipulation, Levitation, and Energetic Hand. The repulsion cantrip pushes objects directly in front of or around the caster (the exact effect depends on the runic components used in the spell’s construction). The weight it can move depends on the caster’s magical strength. It’s one of the rare cantrips that can have a practical effect in battle—pushing enemies away or knocking them off balance.

Gawain knew about this cantrip, but it never occurred to him.

His mind was filled with expanding gases doing work, or high-temperature, high-pressure airflows. Even when the idea of an electric motor briefly flashed through his thoughts, he never connected it to the world’s most basic “repulsion cantrip.”

Watching Rebecca enthusiastically lay out her ideas, Gawain couldn’t help but reflect on himself with a touch of self-mockery—

Don’t overestimate the “transcender’s” broad thinking and otherworldly experience. Those insights can sometimes work wonders, but often they become shackles and stumbling blocks. Like this time: Gawain Cecil’s memory included the repulsion cantrip, so why didn’t he think of it?

Because his mind was stuck on Earth’s classic engine models…

Rebecca had never seen a steam engine, didn’t know what an internal combustion engine was, and didn’t even understand why Gawain insisted on putting a sealed cylinder inside a machine. So her thinking wasn’t limited by those concepts—she just needed Gawain to propose a general idea, then add her own sharp mind and the world’s magical knowledge to come up with a better solution.

Of course, a big part of this was Rebecca’s exceptional talent. With her forward-thinking ideas, she could have been a great figure in this world—someone remembered in history books for at least two class periods—if she hadn’t starved to death first. But one thing was clear: otherworlders aren’t stupid.

They just haven’t thought in that direction yet.

Hetty’s mind was also opened by Rebecca’s ideas. She grabbed a sheet of paper and casually sketched runes and lines: “Exactly… the repulsion cantrip is perfect for conversion into a simple magic circle. In fact, many magical devices—like automatically opening doors and common floor traps—use repulsion cantrips to push things. But no one has ever thought to turn this force into a continuously operating, standardized machine… Ancestor, your wisdom and insight are truly unfathomable.”

As she spoke, she handed over the rough sketch.

Gawain felt a cold sweat break out on the back of his neck from Hetty’s praise—he hadn’t even finished his own self-reflection yet…

He took the sketch and quickly noticed it not only outlined several simple repulsion magic arrays but also listed the cheapest material combinations to achieve each effect.

No wonder Hetty was so thrifty—without her, the camp would waste a fortune.

The three of them huddled together, excitedly discussing the repulsion cantrip, the most basic of spells. Rebecca first pointed to the cylinder on Gawain’s original drawing: “If we use the repulsion cantrip, we can get rid of this sealed metal cylinder entirely, or at most keep a simple guard to prevent debris from falling in. No need for such a tight seal.”

“We can carve the repulsion magic array onto one end of this base to push the part called the ‘piston,’” Hetty chimed in, her curiosity piqued. “But how does the piston come back after being pushed away?”

“By inertia—the inertia of this iron wheel, called a flywheel,” Gawain pointed to the flywheel connected to the piston. “It’s linked to the piston by a crankshaft. When the piston moves away from the repulsion array, the flywheel spins and resets the piston.”

Amber had been staring blankly for a while, initially not understanding. But as the three discussed, she began to catch on. The machine’s basic principle wasn’t complicated—it was mostly a collection of simple wheels and connecting rods. As a thief, Amber was familiar with various traps and mechanisms, so wheels and rods weren’t foreign to her. Hearing them talk about the piston’s return, she quietly remarked, “When the piston moves back toward the repulsion array, the array is still pushing it away—but the big wheel has to finish its last half turn before it can push again. So the machine is basically fighting against itself, right?”

“Exactly…” Hetty frowned. “The repulsion array is needed to push the piston away, but when the piston returns, the array cancels out useful power…”

“‘Useful power’ is called ‘work,’” Gawain seized the chance to share some familiar terms and had already thought of a way to solve the machine’s self-conflict. On Earth, four-stroke engines vent exhaust to relieve cylinder pressure during piston return. For this machine, he needed the repulsion array to stop operating the moment the piston started returning. “A rune trigger—we can use a rune trigger to control the repulsion array. When the piston moves away from the base, the trigger connects; when the piston returns, driven by the flywheel, the trigger disconnects…”

Hetty’s mind filled with magical symbols: “But how to control it? The flywheel spins fast, the piston moves quickly, and the magic has to switch the rune trigger instantly. That requires advanced runes…”

Before she could finish thinking, Rebecca casually said, “Just tie the rune trigger to the piston. When the piston’s near the base, the base is connected; when it’s pushed away, it disconnects. Near, push away, near, push away… boing, boing.”

What kind of mental image made her say “boing, boing”?

Hetty and Gawain stared at Rebecca—Hetty amazed by the elegance of the solution, Gawain marveling at how this scatterbrained girl was a natural science genius. How did she switch seamlessly between magical and mechanical knowledge, instantly leap out of their current train of thought, and find results in a new direction? Did her brain never need to cool down? Or did these two knowledge streams run simultaneously, and whichever came up with a solution got used?

Rebecca shrank back under their gaze. “Did I say something wrong?”

“No, no, no, that’s a great idea,” Hetty quickly waved her hand. “And I thought of more: why only carve one repulsion array? The piston moves back and forth, so we can carve repulsion arrays on both ends of the power unit. That way, the piston gets pushed twice per cycle…”

Gawain studied the sketch seriously, thinking about the rune trigger’s placement. Suddenly, he had an idea: “Also, fixing the rune trigger on the piston isn’t ideal—it means it only connects for an instant each cycle. We can attach it to the flywheel’s axle and have it control both rune arrays on the piston’s ends. Using a ‘toggle’ device, the trigger switches the magical circuit it’s connected to. So, during the flywheel’s first half turn, the rune connects to the first array; during the second half, it switches to the other array. This way, the first repulsion array pushes the piston all the way out, then shuts off as the second array activates to push it back. What do you think?”

Rebecca’s mouth hung open. She looked at Hetty, then Gawain, and suddenly pouted in frustration: “I guess I’m still the dumbest…”

“You’re not dumb at all!” Gawain was both amused and exasperated by her habitual self-doubt. “You’re the one who opened the door to the repulsion array idea. Hetty and I just hammered out the details.”

Rebecca kept pouting. “But the idea for this machine still came from you, ancestor.”

“Without your inspiration, this machine would’ve stayed just a drawing forever,” Gawain laughed. “Don’t you think you’re pretty amazing?”

“Really?”

Gawain and Hetty nodded, smiling. “Really, really.”

“Oh!”

“By the way, ancestor, have you named this device yet?” Hetty suddenly remembered. “For something so new… you have the right to give it a name.”

“A name…” Gawain pondered, and a word came to mind. “Let’s call it the Mana Engine.”

Hetty smiled at the unfamiliar, oddly constructed term. “Ancestor, that’s a great name.”

Rebecca nodded enthusiastically. “Yeah, I don’t know what it means, but it sounds cool!”

Watching his two “granddaughters” caught up in excitement and joy, Gawain lowered his head to his sketches, a new thought forming in his mind:

Could this structure be improved further?

Or rather… now that we have the repulsion arrays and rune triggers as a foundation, could we build something simpler, more advanced, with a completely different architecture?

For example, like an electric motor driven by electromagnetic force, what if we eliminated the pistons, connecting rods, and crankshaft altogether, and instead engraved repulsion arrays at specific angles onto the ring-shaped casing to directly propel the magic-conducting rotor inside?

(End of chapter)