The sound was a physical thing. A low, deep-bass THUD… THUD… THUD… that was so powerful it was less a sound and more a vibration, a rhythmic concussion that I felt in the soles of my boots and the cavities of my chest. It was the sound of a god knocking on the door of his own dungeon.
"It started two days ago," Garr had said. "Right after they sealed the surface. It hasn't stopped."
My blood, which had been a chaotic mix of fear and adrenaline, turned to ice. Two days ago. Right after I had brought Nara back. Right after Krauss had learned that his prison was leaking.
He wasn't drilling to find us. We were a symptom. He was drilling to get to the disease. He wasn't just trying to recapture the "blight"; he was going to sterilize the wound. He was going to purge the Core Foundation itself.
"He's not searching for us," I whispered, the words a horrified revelation. "He's trying to get back into the prison. He's going to kill it. He's going to kill the source."
Garr looked at me, his face pale and slick with sweat in the dim, green glow of his chem-light. "What's the difference? We're living on the roof of that prison. If he breaks it, what happens to us?"
I didn't have an answer. "We have to see it," I said, my voice now as hard and as cold as the tunnel wall. "We have to know what he's doing."
Garr hesitated, his suspicion warring with his own, very real fear. "The Matron said to show you the way," he finally grunted, his voice a low growl. "Not to get us both deleted. These are the old Founder-ways. The air is bad. The code is... thin."
"I can handle it," I said, pushing past him into the narrow, ancient tunnel. "Just lead."
The journey that followed was a descent into the city's forgotten past. The tunnel was no longer the crude, damp, rust-eaten artery of the Undercity. This was Founder work. The walls were made of smooth, perfectly jointed black stone. There was no mildew, no water. The air was dry, hot, and thrummed with a low, oppressive energy. The THUD… THUD… THUD… was no longer a distant vibration. It was our heartbeat. It was the only sound in the world.
We moved in silence for what felt like an hour, the tunnel sloping ever downward, coiling in on itself, leading us to the literal, geographic center of the city's foundation. The heat intensified, and the air took on the sharp, metallic tang of hot metal and ozone.
Garr, for all his bravado and knowledge of the Undercity's "cracks," was out of his element here. He was just a man with a pipe, walking in the guts of a machine he didn't understand. He kept glancing nervously at the walls, at the thick, dormant power conduits that were embedded in the stone like the ribs of a dead giant.
But I... I felt something new. The caged echo of Helias Rogue inside me, the sealed power, it was... thrumming. It wasn't raging. It was resonating. It was responding to the power around me, to the very foundation that Krauss had built. I could feel the city's data-structure here in a way I never had before. I could sense the high-voltage power lines, dormant but for a trickle. I could feel the weak points in the data-wards, the places where the code was, as Garr had said, "thin."
I put my hand on his shoulder, and he flinched, spinning, his pipe raised.
"Hold on," I whispered. "Don't move."
"What? What is it?" he hissed, his eyes wide.
"A ward," I murmured, my gaze fixed on a seemingly solid section of the wall ahead. "A proximity trigger. An old one. But it's still active. If we walk past it, it'll signal the Core."
Garr stared at the blank wall, his face a mask of confusion. "How do you...?"
"I can feel it," I said, my voice barely audible. "The air is… 'louder' there." I reached into my pocket and pulled out the small, rusted bolt Nara had been given, the "gift" from her worshipper. I tossed it underhand. It clattered onto the floor, ten feet in front of us.
The moment it came to rest, a shimmering, blue web of energy, a data-field, erupted from the walls, instantly vaporizing the bolt into a cloud of glowing pixels.
Garr's blood drained from his face. He had been about to walk right into it. He looked at me, his suspicion replaced by a new, grudging, and terrified respect. "Ghost-man," he muttered. "You lead."
I was the scout again. But this was not Krauss's mission. This was my own.
I took the lead, my senses extended, my hand outstretched. I was no longer just walking. I was reading the world. I was feeling the data-flow, the invisible traps, the sleeping sentinels of the city's immune system. I guided us through a maze of dormant laser grids, pressure plates, and data-wards for another twenty minutes, the THUD… THUD… THUD… growing from a heartbeat to a deafening, all-consuming roar. It was the sound of a mountain being rhythmically punched, and it was coming from directly below us.
We finally reached a small, circular room. A ventilation hub. A massive, circular, iron grate was set into the floor, and through it, a blinding, white light pulsed in time with the rhythmic slamming. A wave of intense, dry heat washed over our faces.
Garr and I crept forward, our hearts hammering in sync with the great machine below. We lay flat on our stomachs, peering down through the grate.
My breath hitched. My mind, which had been braced for something terrible, simply... stopped.
It wasn't a tunnel. It was a cavern. A new, massive, perfectly circular chasm, freshly carved from the bedrock, a mile beneath the city. It was lit as brightly as the spire, a blinding white sphere of pure, industrial light.
And in the center of it was the source of the sound. It was a drill, but it was a drill in the way a god is a man. It was a golem, a machine, a temple of pure, focused force. It was the size of the entire Builder's headquarters, a monstrous, multi-limbed construct of black iron and glowing conduits. Its entire upper torso was a single, massive piston, which it was slamming, over and over, into the floor of the cavern.
THUD. THUD. THUD.
And it wasn't alone.
Krauss was there. He stood on a high, carved platform, his arms crossed, a silent, unmoving god watching his creation perform its terrible, world-breaking work. He was not alone. Valerius stood guard at the base of the platform, his obsidian shield a black hole in the white light. Fen was there too, directing a dozen smaller, golem-like automatons that were carting away the tons of shattered rock.
This was the full, focused might of the Builder Faction.
They weren't searching for the prison. They were excavating it. They were going to dig it up, the whole, screaming, blighted thing, and expose it to the light.
My gaze followed the drill's target. It wasn't aiming randomly. It was hammering at a single point, a spot on the floor that was already fracturing, a dark, star-shaped crack that was spreading with every impact. And from those cracks, a faint, dark... mist... was beginning to leak. A visible corruption.
Krauss's logic was terrifyingly clear. He hadn't just sealed the blight. He had built his city on top of it, using its energy, maybe, like a geothermal plant. But now, it was leaking. Nara was the proof. His "necessary sacrifice" was failing. And his solution wasn't to patch the leak. His solution was to demolish the entire power plant, consequences be damned.
He was going to kill the Foundation. And we, the Undercity, were living on the roof of the reactor he was about to blow.
"He's... he's insane," Garr whispered, his voice trembling, his tough-guy facade completely gone. "He'll kill us all. He'll bring the whole city down."
"No," I whispered back, my eyes locked on the scene, my mind racing. "He's the Builder. He'd account for that. He's not trying to destroy the city. He's trying to... to... lance the boil."
I watched, horrified, as a new figure moved into the light. Elara.
She was standing near the drill, her hands outstretched, her violet eyes glowing with a power I had never seen. She was shielding the drill, her own data-weaving magic protecting the machine from the very blight it was trying to reach. She was the surgeon's protective glove.
And then, she stopped.
Her hands, which had been moving in a fluid, complex pattern, froze. Her head, which had been bowed in concentration, snapped up.
Her glowing, violet eyes, now wide with alarm, scanned the cavern. She wasn't looking at the drill. She wasn't looking at Krauss. She was looking at the shadows, at the walls, at the ceiling.
She was looking... right at us.
Not at us, not directly. But at our hiding spot. She couldn't see us. But she could feel us. Our presence here, our terror, our hostile intent... it was a new, unexpected variable in her perfect, controlled equation.
Garr saw it too. He tensed, his hand gripping his pipe.
Elara turned to her master. Her voice, amplified by her own magic, cut through the din of the drill, a clear, sharp, and terrifying bell of alarm.
"Master. The data-flow... it's fluctuating."
Krauss's head turned. The drill stopped. The sudden, deafening silence was more terrifying than the noise.
"There is an unauthorized presence," Elara's voice echoed in the vast, dead quiet. "Something... something is listening."