The drumbeat pulsed through the cathedral's ancient stones like a diseased heartbeat. Elias pressed his palms flat against the cold floor, feeling the vibrations travel up his arms. Each thud sent a fresh wave of nausea through him—it wasn't just sound. It was something alive. Something hungry.

Lira's boot connected sharply with his ribs. "Up. Now." Her voice was steel wrapped in smoke. "That's not a drum."

As if to prove her point, the next pulse came wetter, thicker. The walls wept reddish-black fluid between the cracks in the mortar. Elias's backpack jerked violently, the box inside straining toward the sound like a dog catching scent.

Sister Rosa's voice echoed down the corridor, shrill with panic. "Seal the—" The rest was cut off by a sound like a thousand sheets of parchment being torn at once.

Lira didn't hesitate. She grabbed Elias's collar and dragged him into a side passage so narrow his shoulders scraped both walls. The darkness here was absolute, the air thick with the scent of mildew and something older—dried blood and candle wax.

"Where—"

"Shut up." Lira's hand clamped over his mouth. Her palm tasted of gunpowder and lemongrass. "Listen."

The drumbeat had changed. No longer a steady rhythm, but a stuttering, uneven cadence. Like a heart learning to beat again after centuries of stillness.

Then the whispers started.

Not from the walls. Not from the darkness.

From inside Elias's skull.

"Little guardian..." The voice was honey poured over broken glass. "You've been feeding me such interesting things."

The box in his backpack grew heavier, its weight shifting unnaturally. Elias's vision doubled—for one horrifying second, he saw through two sets of eyes. His own, and something else's. Something that watched from inside the box, through that slit-pupiled eye from his dream.

Lira's knife flashed in the dark, the edge pressed under his chin. "Fight it." Her breath was warm against his ear. "Or I'll cut your throat before it can use you."

Elias gasped, the connection snapping. His knees hit the stone floor hard. "It's...learning. From what it eats."

Lira's expression could have curdled milk. "And you just fed it a Firebrand. Congratulations." She yanked him upright. "Move. The catacombs."

They emerged into a circular chamber Elias had never seen before, though the cathedral had been his second home for years. The ceiling arched high above, lost in shadow. Twelve niches lined the walls—eleven occupied by skeletal figures in varying states of decay, each seated on simple wooden chairs. The twelfth niche stood empty, its chair pristine. Waiting.

The drumbeat stopped.

Silence fell like a guillotine.

Then—

Crack.

The sound came from beneath Elias's feet. The stone split in a jagged line, revealing darkness below. Not empty darkness. Something moved down there. Something that reflected the dim torchlight in thin, vertical slits.

The box in Elias's backpack screamed.

It wasn't a sound. It was a pressure, a force that slammed into his ribs and sent him crashing against the wall. Lira was shouting, but her voice came muffled, as if heard through layers of wool. The skeletal guardians rattled in their niches, jaws clacking in silent laughter.

From the fissure, a hand emerged.

Not bone. Not shadow.

Flesh—pale and perfect, the nails trimmed and clean. It gripped the edge of the broken stone, tendons flexing as it began to pull.

Lira's machete took the hand off at the wrist.

The severed limb dissolved into black smoke before it hit the ground. A howl erupted from below, shaking dust from the ceiling. Lira didn't wait. She grabbed the back of Elias's shirt and hauled him toward an archway hidden behind the niches.

"Run. Don't look back."

Elias ran. The box thrashed in his backpack, its weight shifting like a living thing trying to steer him. Behind them, the chamber collapsed in a roar of shattered stone and something worse—a wet, chuckling sound that followed them into the tunnels.

The passage sloped downward, the air growing thicker with each step. The walls here were carved with symbols that made Elias's eyes water—older than the cathedral, older than the Spanish who built it. Primordial.

Lira skidded to a stop so abruptly Elias slammed into her. Ahead, the tunnel ended at a sheer drop. Below, black water churned in an underground river.

"Hold your breath," Lira said.

"What?"

She shoved him over the edge.

The water hit like a slap from a frozen hand. Elias's lungs seized as the current grabbed him, twisting his body like a rag doll. The box's weight threatened to drag him under, but then—

A hand closed around his wrist. Lira's face appeared in the murk, her braid floating around her like seaweed. She pulled, and Elias kicked, following her toward a faint glow.

They broke the surface in a cavern lit by bioluminescent fungi clinging to the walls. The air smelled of salt and something metallic. Elias coughed up brackish water, his arms shaking as he hauled himself onto a rocky ledge.

Lira collapsed beside him, her chest heaving. "Welcome," she gasped, "to the Hollow King's back door."

Elias rolled onto his back. The cavern ceiling arched high above, studded with stalactites that dripped rust-colored water. And there, carved into the far wall—

A door.

Not stone. Not wood.

Something that looked like bone grown into the shape of an archway. The surface pulsed faintly, as if breathing.

The box in Elias's backpack gave a contented hum.

Lira sat up slowly, water streaming from her clothes. "Well," she said, voice raw. "Now you know why the other guardians died."

Elias stared at the living door. At the way the veins in its surface throbbed in time with his own heartbeat. "They tried to open it."

Lira's smile was a grim thing. "Worse." She pointed to the base of the door, where eleven sets of skeletal hands still pressed against the bone-white surface. "They succeeded."

The box chose that moment to speak again, its voice slithering into Elias's mind:

"Shall we greet our King together, little guardian?"