When the ear-piercing thud of the heavy steel door echoed through the room, Kael took a deep breath. He felt deeply uncomfortable in the dark, form-fitting suit that tightly encased his body. He tugged at the collar that reached all the way up to his neck.

  He could barely make out his surroundings in the room's dim light. There was another door right across from him. To his right was a blank wall, and to his left, a wide, one-way mirror—he knew he was being watched from behind it. Kael slowly walked toward the glass, stood hesitantly in front of it, and stared at his own reflection.

  He examined how tightly the dark fabric gripped him. Turning slowly in place, he studied his silhouette and the suit from the corner of his eye. After standing motionless for a moment, he reached his right hand to the back of his neck. He traced the tough, leathery ridge that extended all the way down his spine with his fingertips. Even though this alien texture still felt unnatural with every touch, it now felt like a part of his own body.

  A deep, resonant voice echoed through the room, its vibrations felt deep within his marrow.

  "Candidate Kael."

  Though Kael realized the voice was coming from a corner of the ceiling, he couldn't pinpoint the exact source. It wasn't a familiar voice. He slowly backed away from the mirror, raised his head, and scanned the dark corners of the ceiling.

  "Welcome to the Threshold Test." The unsettling voice from above was briefly interrupted by a metallic crackle. "We can assume you have many questions. However, you have successfully advanced to this stage."

  Kael swallowed hard.

  "Please listen carefully to the instructions provided." Because of the room's acoustics, the voice felt as if every word was being carved directly into Kael's brain. "The door in front of you will open shortly. We want you to step inside. The purpose of the test is to measure your reactions and emotional fluctuations in challenging situations you may encounter, based on fundamental procedures."

  Kael shifted his gaze from the dim ceiling to the mirror where he knew he was being watched, trying to focus on the darkness behind the glass with a questioning expression.

  That soulless, metallic voice from above abruptly cut off. Following a brief crackle from the speakers, a much more familiar, monotone voice echoed off the walls. Doctor Hestia had likely taken the microphone at the control panel behind the mirror.

  Right then, Kael felt the metallic cuff wrapped around his left wrist vibrate. He raised his arm and looked down at the bracelet-like device. There was a small black screen on the metal surface. Faint green numbers appeared on the display: 64 BPM.

  "The rule is simple." The doctor's voice seeped into the room like a whisper. "If your heart rate exceeds eighty beats per minute, or if you create excessive vibration inside, your wristband will turn red. This means the Carcids have heard or noticed you. In short, Red means you have failed the test."

  Kael swallowed, shifting his gaze from the screen to the mirror on his left.

  "Red... means death."

  The low hum from the ceiling faded, and the room was plunged into a deafening silence. Kael shifted his eyes back and forth between the metal cuff's screen and the smooth-surfaced door standing before him. Unaware of what awaited him just beyond the threshold, he simply stood his ground.

  My heart rate must not rise, he told himself once more.

  After a brief moment, faint clicking sounds began to emanate from the smooth door in front of him. Immediately after, the heavy door began to rise upward with a hydraulic hiss, like the jaws of a monster slowly opening.

  An icy, gentle draft struck Kael's face from within. Beyond the doorway lay absolute darkness, a place where even light didn't dare to enter. Kael saw the number 64 on his left wrist quiver and climb to 68.

  Calm down.

  He took a deep breath and stepped through the door, taking his first stride into the darkness. Once inside, he could see absolutely nothing. The only thing he could perceive were the faint beams of light slipping through the doorway behind him. As he advanced a little further into the blackness, the heavy door slammed shut with that same loud thud, completely isolating him from the outside world.

  Now there was only one truth.

  The darkness, and the dim green numbers glowing like a flicker of hope on his wrist.

  Immersed in absolute darkness, he felt profoundly helpless. No matter which direction he walked, he encountered nothing. Instead, with every step, he felt the texture of the floor gradually changing. What he was walking on was no longer a metallic surface; it felt like a living organism stretched tight with thin skin.

  His eyes should have adjusted to the dark by now, but let alone the room, he couldn't even see his own hands. The only proof he hadn't gone blind was the faint green numbers leaking from the wristband on his left arm.

  72 BPM.

  Kael attempted to take a deep breath, but the air filling his lungs was heavy with the stench of rusty metal and stale blood. The moment he inhaled, his stomach churned, making him feel as though he might throw up.

  73 BPM.

  Right then, right next to his right ear, he heard a whisper, as if someone was standing right there.

  "Stop breathing, Kael."

  The voice was so close that Kael felt the draft created by the whisper against the skin of his right ear. Startled, he spun to his right—at least, he hoped it was his right. His gaze, cast into the darkness, hit nothing but void. No one was there. Or rather, he couldn't see anyone.

  76 BPM.

  The soft, skin-like floor beneath his feet suddenly began to quiver. He felt as though he were standing not on the floor of a room, but atop a colossal, beating heart. He lost his balance and fell face-first to the ground. The moment his skin touched the cold surface, he felt utterly lost. He wasn't sure what his next move should be.

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  78 BPM.

  Don't think, he ordered himself. It's just a test. None of this is real.

  But that rusty metal stench was much stronger now. It felt as if it was coming from right in front of him. He could hear the deep-throated growl of the thing ahead, a sound that shook a person to the core. He didn't want to stand up. Whatever that thing was, he couldn't let it notice him.

  Still resting on the pulsating floor, he used his hands to push himself backward, trying to get as far away from the creature as possible. But nothing changed. That sharp stench continued to burn his throat, and the invisible entity kept advancing toward him, as if tracking his every move.

  79 BPM.

  The wristband began flashing orange in the middle of the pitch blackness, as if desperately trying to issue a warning. Kael realized that crawling backward changed nothing; in fact, it was drawing the thing even closer. Moving, breathing, even fearing—each was leaving a trail for the invisible threat.

  Stop moving, a voice whispered from the depths of his own mind.

  Kael lifted his palms from the throbbing floor, brought them to his face, leaned forward, and squeezed his eyes shut; there was no point in keeping them open anyway. He rejected the heavy, rusty metal smell filling his nose. He exhaled the air in his lungs slowly, millimeter by millimeter. He imagined himself not as a living boy in the middle of a room, but rather as a dead corpse, a machine completely drained of power.

  78 BPM.

  The growl stopped right in front of him. He could hear the dry, clacking sounds the thing's needle-pointed limbs made with every strike against the floor. It was so close he could feel the invisible hunter's appendages standing right beside him. Kael felt the wet, disturbing draft blowing from the unseen creature's mouth onto his face. Kael had gone rigid as stone. He didn't twitch a single muscle, nor did he rush his next breath.

  75 BPM.

  The orange hue on the wristband slowly faded, giving way once again to that safe, cold shade of green. When Kael finally silenced the endless, deafening fear inside him, the clatter of the invisible predator's needle-like limbs gradually drifted away. As the growls dissolved into the dark corners of the room, that throat-burning, dense odor began to dissipate.

  69 BPM.

  The absolute darkness still seemed to seep into Kael's soul. However, for a brief moment, he found a sense of peace. He felt his warm blood slowly circulating back through his body.

  66 BPM.

  Kael felt a vibration in his wristband. He raised his left arm and turned his gaze to the metal cuff's screen. The numbers displaying his pulse were no longer there.

  "Threshold Test complete. Resonance check successful. Lights are turning on."

  The screen blinked with a much brighter, more intense green light.

  Reading the text on his screen, Kael let out a deep breath. But the change in the room following the "Lights are turning on" prompt wasn't what he expected. Kael let out a deep breath as he read the message on the screen. Yet what happened in the room when the words “Lights are turning on” appeared was not what he expected. He thought the darkness would vanish all at once, flooding the room with light—but it didn’t.

  First, a spotlight burst to life directly above him. The beam was so harsh and blinding that Kael instinctively squinted, raising a hand to shield his eyes. For a moment he stood alone beneath that single light, like a figure caught in the center of a stage.

  As his eyes slowly adjusted to the brightness, he realized other lights were appearing around him. One after another, spotlights ignited across the chamber, pushing the darkness back in scattered fragments.

  Then the powerful ceiling lamps came alive. In an instant, the entire room was drowned in a stark, merciless white light—so bright that not a single shadow had anywhere left to hide.

  Kael shielded his eyes with his hands. The first thing he noticed was that the "living" floor he had just walked and crawled upon was, in fact, nothing but cold, gray metal. There was no trace of a rusty stench, nor any growling predator. The room was entirely empty.

  Or so he thought.

  As his eyes acclimated to the blinding white, he realized he wasn't alone in the massive expanse of the room. Kael shuddered; right next to him was a boy, kneeling just as he was, drenched in sweat. A little further away, another boy was looking around in sheer terror, as if he had shared the exact same fate. But the most shocking sight of all was the roughly twenty children scattered across the room, each looking as if they were locked inside their own invisible cage.

  They were all there. Twenty Alpha candidates; in that pitch-black darkness, lost in the labyrinth of their own nightmares, they had brushed past one another, felt each other's breaths, yet had been left completely isolated by the flawless acoustic illusions generated by the facility.

  An indescribable emotion washed over Kael. He felt relieved, but it wasn't a peaceful feeling. It was that uncanny comfort born from realizing he wasn't the sole victim of a catastrophe.

  The children gradually grew accustomed to the room's blinding light, beginning to stir where they stood and moving toward one another. Kael scanned every inch of the room with his eyes, trying to find a familiar face. He knew the people around him, but he didn't feel close to any of them; they were all just shadows carved by the same discipline, carbon copies of each other.

  Then he saw Tarin. He was sitting on the floor, staring at the ground with empty eyes, like someone who had survived a disaster but hadn't quite overcome the trauma. Kael walked over to him with quick steps.

  "Tarin? Did you... Did you hear those growls too?"

  Tarin didn't tear his gaze from the floor. His voice was like a whisper. "Growls? No... Everything was burning, Kael. The people, the cities... I felt my skin scorching."

  He couldn't find a word to respond to Tarin's trembling voice. The menacing sounds of the predator he had heard paled in comparison to Tarin's hell.

  He kneeled down next to his friend and offered him a hand. After a moment, Tarin shifted his gaze to Kael. The traumatized expression on his face was horrific, yet a faint smile appeared at the corner of his lips. He took Kael's hand, and they stood up together.

  As Tarin brushed off his clothes, he studied his friend. "You look like you weren't affected at all."

  "You wouldn't have wanted to be in my place. It got close enough to touch me." Kael's gaze drifted into the depths of the room.

  "I'm sure it must have been curious about how you taste." Tarin chuckled softly and placed a friendly hand on Kael's shoulder.

  All the whispers inside the room suddenly ceased.

  "Congratulations, candidates."

  That unnerving voice echoing from the depths continued.

  "You have passed the Threshold Test. Please proceed to the exit."

  After the announcement ended, a loud, mechanical noise rose from the far corner of the room. One of the heavy doors ahead had opened.

  All the children moved toward the exit at a slow pace. Kael scrutinized the other kids walking around him with a thoughtful gaze.

  I wonder what they faced?

  While these thoughts occupied his mind, that familiar scent suddenly struck his nose. He could feel someone following him very closely, right behind him.

  He slowed his steps and looked back over his shoulder.

  Mira was right behind him.

  She looked utterly flawless and expressionless, as if she hadn't just been fighting for her life in that absolute darkness like everyone else. There didn't seem to be a single speck of dust on her form-fitting suit. As she pulled level with Kael, she didn't slow her pace; she merely turned her gaze toward him. At that moment, Kael's eyes caught the dull green screen on the girl's wrist.

  44 BPM.

  "Your heart was giving you away, Kael," Mira whispered. She wore a subtle smile on her face. "Real predators won't be as merciful as they were in this simulation."

  Before Kael could even respond, Mira gave him a slight nod of encouragement and glided past him.

  Kael stepped out through the open metal door and into the dim light of the corridor. He swallowed hard. For the first time, the number 69 on his own wristband felt less like an achievement and more like a weakness.

  As the children moved a little further down the corridor, they came face-to-face with Marshal Voss, who stood waiting like a statue.

  "The Threshold Test is over," Voss bellowed, his voice loud enough to jolt every exhausted body.

  "You maintained your composure against the tricks of your own minds. You did what every Alpha candidate is supposed to do." Following his words, Voss scrutinized the candidates lined up before him with sharp eyes. "But this was just a warm-up. Now return to your quarters and rest."

  Voss's face resembled a cold slab of rock. "Tomorrow, we will proceed to the Field Adaptation Test."

  Voss took a step forward. He stared directly into the eyes of the exhausted candidates looking back at him.

  "This time, the threats you face will be far more challenging. You must prepare yourselves for that.”