Low-Fantasy Occultist Isekai

Nick crouched beside the nearest carcass, flipping it over to expose its underside. He prodded the charred flesh, finding the skin was tougher than it looked. Thankfully, his dagger was sharp enough that he didn't need to apply much pressure.

Making a clean incision along its belly, he peeled back fur and skin to reveal the innards beneath. His brows furrowed in concentration as he sifted through the remains, pushing aside organs with the tip of the blade, looking for the glimmer of mana he could still feel.

"There," he muttered under his breath, spotting a small, irregular shape nestled near the base of the spine. Using the point of his dagger, he teased it free, revealing a scraggly, muddy green stone no larger than a fingernail. Its surface shimmered faintly, almost pulsing with an inner light. Holding it up to the light, Nick felt an immediate draw—a concentrated well of mana radiated from it, faint but unmistakable.

"What is that?" Elia asked, crouching beside him. Her eyes flicked between the stone and the open carcass. "Wait, are you done with that squirrel? Can I have it?"

"Sure," Nick replied absently, focusing entirely on the strange object in his hand. He turned it over, studying the way its surface caught the light. There was mana within, that much was undeniable, but why was that? "This feels like a bezoar," he murmured, thinking aloud. "But for magical creatures instead of animals."

Elia, already distracted, grabbed the squirrel and carried it off with a satisfied hum. Meanwhile, Nick's thoughts raced. In his limited understanding, bezoars were formed as natural antidotes in the stomachs of certain animals through constant calcification of ingested matter. But he'd never seen or heard of anything similar in magical creatures. Thinking back to his family's hunt for the thunderhoofs, he couldn't remember finding anything of the sort, and his parents hadn't mentioned it was possible, even in passing.

Technically, there could have been one in the troll. We didn't butcher it ourselves, and its skin was resistant enough to disturb my senses. Not that I looked too deeply. That thing stank.

Still, something told him he wouldn't have found one. No, the only possible answer lay in Roberta's diary. The passages describing mutated creatures deep within the Green Ocean came flooding back. Those beasts often had excess mana running rampant through their systems, warping their forms and abilities. Could this be related? Was this stone the byproduct of such a mutation? He had no time to dwell on the thought before Rhea's voice cut through his musings.

"Wait… is that what I think it is?" she asked, stepping closer. Her eyes widened as she got a better look at the stone. "Sashara help us, that's a mana core."

Nick raised an eyebrow. "A mana core?" He could imagine what she meant, but having someone with a good education on hand was proving its worth once again.

Rhea nodded, her expression conflicted. "They're supposed to be found only in really strong monsters." She replied. Seeing that it wasn't enough to appease him, she sighed, "Monsters don't progress like the Fair Races. Their growth and abilities seem to follow entirely different rules, and some have speculated they might have a different System altogether, though the temples don't like that kind of talk. A mana core is rare, even in something strong. And these squirrels…" She gestured to the creatures with a bewildered shake of her head. "They're nowhere near powerful enough to have one."

Nick stared at the core, its faint glow reflecting in his eyes. The idea that the Green Ocean might be undergoing something different from the natural order wasn't new—he had both his own observations and the word of an experienced adventurer to prove it—but seeing it firsthand was something else entirely. Without a word, he slipped the core into his pouch and turned his attention to the other fallen squirrels.

He repeated the process with the next one, careful not to let his curiosity get ahead of him. Sure enough, another core was nestled within its body, identical in size and faint glow to the first. By the time he'd finished with the last of them, he had four green crystals resting in his palm, their light spilling between his fingers like trapped starlight.

"This can't be normal," he muttered, glancing at Rhea. "Four mana cores in squirrels that were barely F-rank creatures. What's going on here?"

Rhea crossed her arms, her expression grim. "I don't know. But cores don't form out of nowhere. Something weird is going on."

A strange, crunching noise interrupted their conversation. Nick and Rhea turned toward Elia, who was sitting cross-legged a short distance away. She was gnawing on a bone; her sharp teeth gleamed as she plucked another piece of meat. The rest of the squirrel she had taken was gone.

"Elia," Nick said slowly, "did you just eat that entire squirrel?"

Elia grinned, canines on full display. "What? You said I could have it."

Nick pinched the bridge of his nose, exhaling heavily. "You know what? Forget it. You are the one who killed them anyway. Let's just move on. We won't find answers here."

Elia shrugged, tossing the cleaned bone over her shoulder. "Are you guys sure you don't want any?" She asked. When she only got two flat stares, she shrugged. "Your loss. It was delicious."

Rhea shook her head, horrified. "Do you even know what kind of diseases you could get from that?"

"I used foxfire for a reason. I'll be fine." Elia waved her off.

Nick chuckled under his breath, pocketing the Cores and rising to his feet. "We don't have time for this. If we're already running into mutated creatures this close to the edge of the forest, it will only get worse from here."

Rhea hesitated but nodded. "Right. Let's keep moving."

The three of them set off again. Nick tried to ignore the nagging thought that he might not be as prepared as he believed.

To avoid becoming distracted from all the theories swirling in his mind, he led the way, keeping his senses peeled for another ambush. Behind him, Rhea glanced nervously at the dense foliage, her right hand hidden in her satchel. Elia followed last, swinging her arms and humming softly.

"We still need to stick to this path for a while," Rhea said a little shakily. "Ogden told me it runs for miles and leads to several hidden spots, but our target shouldn't be more than an hour away."

Nick grunted in acknowledgment but didn't slow his pace.

The further they walked, the older the forest appeared. The trees grew impossibly large, their roots curling like gnarled fingers across the trail, forcing the trio to step carefully. Bright green moss covered everything.

A small stream suddenly cut across their path, gently trickling by. The water was clear, with smooth pebbles visible on the sandy bottom. But Rhea froze in her tracks, her breath catching.

"This… this wasn't here before," she whispered, wide-eyed. "It wasn't. I know this path. There's no stream."

"Rhea," Nick said, turning to face her. She wasn't listening, her panic growing as she muttered under her breath.

"No, no, no. If we're on the wrong path, we'll be lost, and then—"

The slap echoed through the forest, shocking the girl into silence. She looked up at Nick, her cheek red and her mouth slightly open in surprise.

"Focus," Nick said firmly, lowering his hand. "Did we get on the wrong path?"

Rhea blinked rapidly, the panic fading from her eyes. She shook her head. "No, we didn't. This is the right path. I'm sure of it. We never left it."

"Then it's new," Nick said, gesturing at the stream. "It happens. Rivers and streams shift, especially in a place like this. Anything from a natural phenomenon to a magical one could have done this. We just need to continue along. But we're not crossing it until we're sure it's safe."

Grabbing a sturdy stick from the ground, he approached the stream. Kneeling, he poked at the shallow water. Ripples spread outward harmlessly. Next, he levitated a few stones from the bank and hovered them over the surface before dropping them in. They sank with faint plops, disappearing into the sand.

For a moment, all was still. Then, a dark glob of ooze surged upward from the bottom, latching onto the stones and swallowing them whole. The thing expanded, quivering as it reared up, its form amorphous and glistening. The next second, it hurled toward Nick, smacking against the telekinetic barrier with a wet splat.

"Slime!" He shouted, stumbling back but holding the shield steady. The impact strained his focus, especially since it remained there, pushing its whole body against the barrier, but he managed to keep the creature at bay. It wasn't very strong.

The others screamed in surprise; Elia grabbed Nick's arm and helped him up. "What is that thing?!"

Nick didn't answer immediately; his eyes were fixed on the creature. The way it moved, the sheen on its body—it clicked. "Not a regular slime. A river slime," he said through gritted teeth. "Its body is very acidic. It can melt through flesh in minutes but doesn't have many ways to attack if we don't get close. Keep your distance!"

He grunted as the slime pressed harder against the barrier, its surface bubbling and quivering in frustration. Though he felt he could keep it away almost indefinitely if needed, Nick didn't see the need to leave an ambush predator behind them. Bringing his palm up, he conjured a fireball and threw it.

The orb struck true, causing the slime to writhe and bubble. Though the attack didn't seem to hurt it much, the slime visibly recoiled, its form shrinking slightly.

"Fire works, but it's not enough," Nick muttered, sweat beading on his forehead from working three spells simultaneously. [Hoplite's Help] had probably saved him, so he didn't even think about stopping it, but he momentarily wondered if he should have gone through a ritual before he ventured in.

Oh well, I'll do better next time. Now, just how much fire will this thing need to die? He had read it was considered the best element, but it seemed that [Minor Elemental Manipulation] simply didn't pack the punch needed, no matter its recent growth.

Elia stepped forward, her own fireball forming in her hands. Grunting in agreement, Nick moved away, but before she could release it, Rhea stopped her.

"Wait! Fire of this level will only annoy it," Rhea said, rummaging through her satchel. "It'll take too long to kill it that way. Nick, can you keep it still for a few seconds?"

"Yes," Nick replied. The slime repeatedly slammed into the barrier, each impact sending ripples through his field. If it wasn't for [Parsimonia] allowing him to calibrate the mana output precisely, Nick would have feared running out soon, but this was a manageable strain.

It doesn't mean I want to keep at it for long. I doubt this will be the last monster to attack us.

Rhea pulled out a small glass vial filled with a viscous yellow liquid. "This should do it." She stepped cautiously toward the slime, unscrewing the cap. "Just hold it steady."

Nick adjusted the field, forcing the slime into a tighter area and giving Rhea a clear path. She approached with only slight hesitation and tilted the vial. The liquid dripped out slowly like honey. As soon as it made contact, the creature let out a bubbling hiss and streaks of yellow spread rapidly over its surface.

"Get back!" Rhea shouted, and Nick retreated as quickly as he could, pushing more mana into the field. It wasn't the most efficient usage, but it would let it hold better under strain.

The slime began to dissolve, collapsing inward as the yellow liquid ate away at it. A cloud of vapor rose quickly, withering everything it touched. Nick felt gratified by his decision to augment the barrier. Within moments, the slime was gone, leaving nothing but a lump of dirt.

Out of caution, Nick waited an entire minute before approaching, lowering his barrier just enough to get it back up should something attack. He used his dagger to prod the rock, flipping it over to reveal another small, scraggly mana core under the mud. He sighed, calling a small tendril of water from the stream and cleaning it before pocketing it alongside the others.

"This just keeps getting weirder," he muttered.

Elia raised an eyebrow. "So, are we going to start a collection now? I know some kids like marbles, but those don't look like they will roll well."

Nick rolled his eyes but didn't reply. Rhea, still catching her breath, stared at the dissolved remains. "Slimes aren't supposed to have Mana Cores, either," she said softly.

"I suspect we might find out why sooner or later," Nick murmured, adjusting his pouch. Despite his words, he couldn't help but feel intrigued. "Let's keep moving."