The tunnels were the city's digestive tract narrow, damp, and smelling of ancient rust and stagnant mana. Here, the "Static Field" was thinner than in Sector Zero, replaced by the rhythmic, mechanical pulse of the city's core.
Atsu led the way. He didn't use a light. Instead, he relied on his Echo Location a new refinement of his blood-sensing. By releasing a microscopic, high-pressure mist into the air and "feeling" how the vibrations returned, he could map the tunnels with better precision than any mage's scrying spell.
Behind him, Elara, Kael, and four other Unbound moved in single file. The tension was a physical weight. Every drip of water, every scurrying rat, made the mages' hands twitch toward their wands.
"Left at the junction," Atsu whispered, his voice barely audible over the hum of the pipes. "There's a Type 3 monitoring station a hundred yards ahead. If we hit the main conduit, the sensors will pick up your mana-signatures."
"How do you know that?" one of the Unbound, a scarred man named Jax, hissed. "We haven't seen a map in miles."
"The vibration," Atsu replied, his apathetic eyes staring into the darkness. "The resonance of a monitoring station is 60 hertz. The pipes ahead are vibrating at 58. They're being drained. It's an ambush point."
Jax narrowed his eyes but followed. He was the one Kael had called their "heavy hitter," but his movements were too precise, too disciplined. He didn't move like a man who had been hiding in a basement for years. He moved like someone who was waiting for a signal.
Atsu noticed it. His "数字" tattoo was pulsing in a rhythmic, warning pattern.
Calculation: Probability of Internal Breach: 64%.
"Stop," Atsu said, halting the group at a narrow bottleneck where the pipes were encrusted with glowing green mana-residue.
"What now, Yuta?" Kael asked, his violet tattoos flickering. "We're losing time."
"The sensor isn't ahead," Atsu said, turning to face the group. "It's behind us."
He looked directly at Jax.
Jax didn't flinch. Instead, a slow, cold smile spread across his face. He reached into his collar and pulled out a small, silver needle—a high-frequency Communication Link. It was glowing with a steady, Imperial blue light.
"You're as smart as the reports said," Jax noted. "Too bad 'smart' doesn't stop a sterilization squad."
He crushed the needle.
The tunnel behind them didn't explode. It went silent. A sudden, absolute void of sound that could only mean one thing: a Silence Field. From the shadows, four silhouettes emerged, clad in the matte-black armor of the Guild's Spec-Ops.
"Betrayal," Kael spat, his hands erupting in violet fire. "Jax, you bastard!"
"The Guild offered me a pardon and a seat in the Academy," Jax said, stepping toward the Spec-Ops squad. "All I had to do was lead the 'Error' into a corner."
Atsu didn't look angry. He didn't even look surprised. He simply shifted his weight, his fingers brushing the iron dagger at his belt.
"Kael, Elara, get behind the pressure valve," Atsu commanded.
"What are you doing?" Elara asked, her staff sparking with frantic amber light.
"I'm the only one who doesn't need mana to fight in a Silence Field," Atsu said.
The Spec-Ops squad moved with synchronized lethality. They didn't chant; they used Pre-Loaded Runes etched into their blades. They lunged through the silence, their movements a blur of black steel.
Atsu entered Zero-Thinking Mode.
The world slowed. He didn't hear the clash of blades, but he felt the displacement of air. He parried the first strike with the iron dagger, the vibration traveling up his arm. He didn't use his blood not yet. He used the surroundings.
He kicked a mana-conduit pipe, the rusted metal buckling and spraying a cloud of high-pressure, green residue into the air. The Spec-Ops mages, relying on their optical visors, were momentarily blinded by the mana-flares.
Activation: ON.
Atsu didn't spray. He used the Delayed Construct logic. He let a single drop of blood fall onto the floor as he ducked a horizontal swing. As the second mage stepped forward to finish him, Atsu triggered the "Sleeper."
A jagged spike of blood erupted from the ground, piercing the mage's foot and pinning him to the metal floor.
Jax roared, drawing a heavy mace glowing with kinetic energy. "You think a few drops of blood can stop the Guild?"
"No," Atsu said, his voice a ghost in the soundless tunnel. "But the pressure in these pipes will."
He slammed his iron dagger into the main release valve of the mana-conduit.
The explosion was visual, not auditory. A massive wave of raw, unrefined energy flooded the tunnel. For the mages Jax included it was like being hit by a tidal wave of static. Their spells backfired, their runes melted, and their nervous systems overloaded.
Atsu, the "World Error," simply stood there. He was the only thing the energy couldn't touch, because he was already the ultimate disruption.
As the Spec-Ops squad collapsed into unconsciousness, Atsu turned back to Elara and Kael. His "数字" tattoo was now a "2". The evolution was accelerating.
"Jax is dealt with," Atsu said, wiping a smear of green residue from his face. "But the signal went through. The heart of the city knows we're coming."
"Then we stop sneaking," Kael said, his violet eyes burning with a new, dangerous light. "We run."