Chapter 5: Vacuum Flasks and the Conservation of Momentum
Four years slipped by in the Valerius Barony like a quiet, comfortable dream.
By the time Ren turned eight, the crumbling baronial estate had secretly transformed into the most luxurious residence on the continent, though you wouldn't know it from the outside. Ren was careful. To the rest of the world, House Valerius was still a poor, rural noble family.
But inside the manor? It was a hidden utopia.
Ren had used localized earth and water manipulation—guided by modern plumbing schematics—to install under-floor heating and pressurized hot showers. He told his father he had simply "fixed the old pipes," but Martha, the Head Maid, knew the truth. She guarded Ren's secrets with terrifying efficiency, ensuring no outside servants ever entered the inner quarters.
In return, Ren spoiled his inner circle ruthlessly.
It was a crisp autumn afternoon. Ren sat on a checkered blanket in the woods just past the estate's boundary. Beside him sat Elara, now nine years old, growing into a beautiful, sharp-eyed young maid-in-training. On his other side was Kira, whose silver fur was impossibly soft and glossy, her fox-ears twitching happily as she chewed on a piece of dried jerky.
"Master Ren," Kira murmured, leaning her head against his shoulder. "It's cold today. We should go back inside. The heated floors in your room are calling me."
"Just a little longer, Kira," Ren smiled, patting her fluffy head. He reached into his satchel and pulled out a sleek, metallic cylinder. He unscrewed the cap and poured a steaming cup of sweet, spiced tea, handing it to Elara, and then another to Kira.
Elara cupped the tea, her eyes widening. "Ren, it's been in your bag for three hours! How is it still boiling hot? Did you enchant the metal?"
"No magic," Ren said, taking a sip from his own cup. "It’s a vacuum flask. There's a smaller bottle inside the larger one, and I used a tiny bit of wind magic to suck all the air out of the space between them."
"I don't understand," Kira said, blowing on her tea.
"Heat travels through air molecules by bumping into them," Ren explained simply. "If there is no air between the inside and the outside... the heat has nothing to bump into. It’s trapped. Perfect insulation."
Elara stared at the metal cylinder, her young mind racing. Over the past four years, Ren’s "lessons" had become the core of her and Kira's world. They didn't learn standard magic theory. They learned physics.
Suddenly, Kira’s silver ears swiveled backward, standing straight up. The relaxed, sleepy fox-girl vanished, replaced by coiled tension.
"Something is coming," Kira whispered, her amber eyes locking onto the dense brush ahead. "Heavy. Fast."
A low, guttural squeal echoed through the trees. The brush violently parted, and a Razor-Boar burst into the clearing. It was the size of a small horse, covered in iron-hard bristles, with two massive, curved tusks aimed directly at the picnic blanket.
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It was a Tier-2 magical beast. A grown knight would struggle to kill it.
"Elara!" Ren commanded, not moving an inch.
Elara didn't hesitate. She didn't panic, and she didn't chant. She slammed her hands onto the dirt.
Four years ago, she would have tried to build a flat, heavy wall of stone to stop the beast, draining her mana and likely getting crushed. But she remembered Ren’s lesson with the wooden blocks.
Redirect. Don't resist.
A slab of earth shot up from the ground right in front of the charging beast—but it wasn't a wall. It was a perfectly smooth, heavily compacted ramp of stone, angled at exactly forty-five degrees.
The Razor-Boar, weighing over a thousand pounds and moving at incredible speed, hit the ramp. The massive kinetic energy of its charge wasn't stopped; it was violently redirected upward.
With a squeal of confusion, the boar launched into the air, its feet pedaling uselessly as it sailed entirely over Ren and the girls, crashing heavily into the dirt ten yards behind them.
"Kira. Now." Ren said calmly.
The fox-kin girl didn't draw a sword. She didn't use attack magic.
Ren had taught her the conservation of momentum and the structural weaknesses of anatomy. The boar was staggering to its feet, dazed from the fall, its heavy head low.
Kira sprinted. Her Agility stat was already her highest attribute, but she applied Ren's teachings: she leaned forward, minimizing wind resistance, her footfalls hitting at precise angles to maximize forward thrust. She was a silver blur.
As the boar shook its head and locked eyes on her, Kira didn't strike the thick armor on its skull. She leaped, using her forward momentum to pivot around the beast's neck. In her hand was a simple, high-carbon steel dagger Ren had forged for her.
She drove the blade perfectly into the gap between the cervical vertebrae—the exact anatomical weak point Ren had drawn for her on a chalkboard weeks ago. She used the beast's own massive weight and her falling momentum to drive the blade deep, severing the spinal cord instantly.
The Razor-Boar dropped dead without a single cry.
Kira landed gracefully on her feet, flicking the blood from the dagger. She turned back to Ren, her tail swishing proudly, waiting for praise.
Ren clapped his hands. "Flawless execution, both of you. The angle on that barrier was perfect, Elara. And Kira, your kinetic transfer was highly efficient."
Elara blushed furiously, dissipating the stone ramp. "It was easy, Ren. Just like you taught us."
"We will have Martha roast the boar for dinner," Ren smiled, standing up and brushing off his trousers. "I think we can use the fat to make some proper soap, too."
As Elara and Kira celebrated their victory, Ren walked over to the carcass. His smile faded.
He crouched down, examining the boar's hind legs. There were deep, jagged claw marks carved into the thick hide. They were fresh. And they were festering with a dark, purplish mana.
This boar didn't attack us because it was hunting, Ren realized, his high Intelligence stat piecing the variables together instantly. It was running away in blind panic.
He looked deeper into the dark, autumn woods. His Skill Panel suddenly flickered, not with a warning from the System, but with a basic world notification that he hadn't seen before.
[Ambient Mana Density Increasing in Sector 4.]
[Event Trigger: Stampede (Approaching)]
Ren’s eyes narrowed. The quiet, comfortable childhood he had built for his girls was about to be tested. The woods weren't just hiding a few rogue beasts. Something massive was driving them out, and it was heading straight for the Valerius estate.
Ren stood up, turning back to Elara and Kira. His voice was calm, but it carried the chilling, calculated weight of a true Archmage.
"Pack up the tea, girls. We need to go home. We have a lot of defenses to build before your fifteenth birthdays."