The air in the tunnel began to feel thicker and heavier, almost like breathing through a damp cloth.

  A primal warning stirred at the base of their skulls, the kind of instinct older than language and by far older than reason.

  Every step forward made that feeling worse, like they were walking toward something that should not exist.

  The party slowed without anyone needing to say a word. Even their armor seemed quieter as their movements became more deliberate, as if loud noise alone might wake whatever waited ahead.

  After a brief pause, they continued forward.

  Kavisha’s quill resumed its steady scratching across stiff paper, the familiar sound oddly comforting in the oppressive silence only pausing every few steps as her eyes flicked between the tunnel walls, the floor, the faint residue of the rune marks which had been burned nearly to nothing.

  Each observation went into her notebook with precise, practiced efficiency.

  Ahead of them the tunnel curved slightly and should have bent into deeper darkness.

  Instead, a faint glow bled along the stone ahead of them.

  It was initially subtle being just a whisper of color reflecting off wet rock. But with each step, it grew stronger.

  The light pulsed slowly and steadily, like a heartbeat. Its blue glow was not any natural blue as it was too bright.

  At first, Eleonora thought it was just moisture catching torchlight. The sewer air was thick and damp, and the stone often gleamed slick with condensation. With the water beading along mortar seams and running in slow, rivulets down the walls.

  It would have been easy and comfortable, even to assume this was more of the same.

  However, the further they walked, the more the glow swallowed the torchlight, until their flames seemed small and weak in comparison.

  The stone itself began to shimmer.

  Thin veins of that same blue light crawled along cracks in the tunnel walls like frozen lightning. Here and there, patches of the strange glowing residue clung to the rock, thicker than before, slowly rising and falling in lazy, breathing pulses.

  Lucien swallowed hard as suddenly felt sick.

  “The mana density…” he murmured. “It’s climbing.”

  Eleonora and the other party members also felt it too now even though they were not mages. It wasn't just a pressure in the air, but also a faint vibration in their bones, like standing too close to a massive bell after it had been struck or getting shocked by a lightning spell.

  Isadora tightened her grip on her shield, subtly moving to interpose herself between Eleonora and the strange goop.

  Kavisha stopped walking long enough to make three quick, sharp notes before hurrying to catch up again, eyes wide with equal parts fascination and concern.

  The torchlight which should've danced and should’ve stretched the tunnel into shadows as it bent them around corners, and shimmying across the uneven stone no longer did so in the new light.

  A thick, semi-translucent slime coated the stone in wide, uneven patches, like someone had smeared glowing putty across the tunnel. It clung to mortar seams, pooled in shallow depressions, and stretched in thin strands between bricks like webbing.

  In some places it formed drooping curtains, sagging slowly under its own weight. In others it bubbled faintly, releasing tiny, soundless bursts that reformed moments later.

  The tale has been illicitly lifted; should you spot it on Amazon, report the violation.

  It glowed faintly blue green with a color somewhere between deep ocean water and prussian blue as the light brightened… then dimmed… then brightened again. Each pulse was subtle, but once you noticed it, you couldn’t ignore it. It set a tempo in the tunnel, slow and steady, like something breathing in its sleep.

  The glow reflected off the shallow film of sewer water under their boots, turning the tunnel into a dim, underwater nightmare of shifting green-blue light. Their shadows stretched and collapsed with each pulse, making it look like they were moving even when they stood still.

  Eleonora felt the hair rise along her arms beneath her armor. The sensation crawled across the back of her neck.

  “Don’t touch it,” Kavisha said automatically, though no one had moved yet.

  Her voice was low, controlled, but Eleonora could hear the sharp edge of curiosity underneath the caution. Dangerous things had always fascinated Kavisha. Dangerous, rare, and unexplained things even more so. She called out for Lucien to take a closer look.

  Lucien did so like a man approaching a sleeping predator. His movements were slow and careful with every step deliberate. His boots clunked against the damp stone as he moved. Meanwhile the glow reflected across his face, painting his skin in a sickly blue-green color while making the whites of his eyes look almost luminous.

  He raised one hand slightly, not touching it, just feeling the air around the mystery goop.

  “When he got within a few feet of the largest patch, he staggered like a drunk after an all-night binge.

  It hit as a sudden and violent attack of mana poisoning almost as if he’d been punched in the gut by something invisible. His breath left him in a sharp gasp as his knees buckled.

  “Lucien!” everyone called out almost simultaneously as the big orc almost fell over like a great oak.

  Eleonora lunged forward and grabbed his arm before he could fall into the shallow channel running along the tunnel edge. The sewer water there moved sluggishly, carrying bits of filth and drifting scraps of organic waste and now, the faint streaks of that same blue-green glow.

  Lucien sagged against her grip, one hand gripping his staff while his eyes were squeezed shut.

  “Mana,” he rasped, voice thin and tight. “Gods… the mana output…”

  Another pulse of light rolled across the walls, brighter this time.

  Eleonora could swear she felt it not just saw it. Like pressure pushing briefly against her chest.

  Lucien sucked in a shaky breath, trying to steady himself, but his hand trembled as the tunnel filled once more with that slow, breathing glow.

  He braced himself with his staff once more, breathing hard, his face gone pale enough that it stood out even in the sickly blue glow.

  “Mana,” he said, voice tight, like he was speaking through clenched teeth. “Gods… the mana output from that slime is… absurd. Way too high to be natural.”

  Kavisha, meanwhile, was already kneeling beside a patch, studying it like a scholar standing before a priceless manuscript.

  “Color variation…” she murmured. “Outer edges are slightly dimmer. Central mass is more saturated…” She leaned closer, squinting. “Pulsing interval approximately… five seconds? Maybe six?”

  She flipped her notebook open and began scribbling rapidly, her quill scratching loud in the unnatural quiet of the tunnel.

  “Consistency… gelatinous but holding structure… not fully liquid… adhesion is strong…” She tilted her head, watching another pulse of light move through the slime like a slow heartbeat. “Yes. Definitely abnormal.”

  “Kavisha,” Isadora said quietly, “could that be the source of the monsters we've seen down here”

  “I don't doubt especially if it gives off enough mana to give a mage mana poisoning," Kavisha said calmly, not looking up.

  She reached to her belt and pulled free a small glass vial, then a narrow metal spatula no wider than a finger. With careful, almost surgical precision, she scraped a small sample from the edge of the slime patch. The substance stretched before snapping free, sliding into the vial with a wet, unpleasant sound.

  The glow dimmed slightly from where she had removed it ass Kavisha corked the vial tightly, then sealed it with a twist of wax from a small thumb-sized seal stick she kept tucked in a pouch on her belt

  “Eleonora, can you put this in your storage ring please?”, Kavisha asked.

  Eleonora slid her gauntleted thumb across her storage ring, opening the pocket space and causing the air to shimmer faintly above her palm.

  She held her hand out for Kavisha.

  Kavisha dropped the vial inside without looking, already returning to her notes.

  “Good,” Kavisha said. “If this is contaminating the sewer system, it explains the mana spikes.”

  Lucien straightened slowly, still breathing deeper than normal, like someone recovering from altitude sickness.

  Images flashed through Eleonora's mind unbidden of a massive monster scourge pouring out of the sewer and into the city, however almost as if Kavisha could hear everyone's thoughts even though she was just talking to herself, said, “no,” Kavisha said flatly, still writing. “Let’s not finish that thought,” interrupting Eleonora's train of thought.

  She snapped the notebook shut and stood, brushing sewer dust and grit from her knees.

  “We proceed assuming containment is critical,” she continued, voice all business now. “No direct contact. No open skin exposure. If any of you feel dizzy, nauseous, or experience sudden magical surges, you say so immediately. Understood?”

  “Understood,” Isadora said.

  Eleonora nodded. “Yes.”

  Lucien gave a small, humorless smile. “Already experienced the dizzy part. I’ll let you know if I start levitating,” he joked.

  Though no one laughed as they began moving again, slower now, hugging the cleaner side of the tunnel where the stone was still bare.

  The glowing slime appeared more frequently as they went. In thin streaks at first, then wider patches, then entire stretches of wall veiled in that slow, breathing light.