Coming down from the verdant Iron Tree Hell, Slayer felt like he had walked into a giant kaleidoscope.

  Light. Refracted light everywhere.

  Fourth Layer: Mirror Hell.

  There was no ground here, no sky. Only countless mirrors suspended in the void. They varied in size; some were as small as a palm, others as huge as skyscrapers. The mirrors were connected by some invisible light paths, forming a complex maze.

  Every mirror played a different scene.

  Someone stealing, someone killing, someone helping an old lady cross the street.

  This was the Big Data Center of the Underworld, recording every move of all beings in the Three Realms.

  But now, this place was occupied by a type of demon called "Prism Demon."

  These demons were entirely made of crystal. Not only could they turn invisible in the reflections of the mirrors, but they could also use the mirror surfaces to reflect Slayer's attacks.

  Pew—!

  A red laser beam suddenly shot out from a mirror on the side, heading straight for Slayer's head.

  Slayer reacted extremely fast, tilting his head. The laser grazed his helmet and shattered a small mirror behind him.

  [Warning: Optical Camouflage Unit Detected.]

  [Warning: Cannot Lock Target Position.]

  Slayer raised his shotgun, but he didn't fire.

  Mirrors were everywhere. If he fired, the pellets might refract dozens of times and end up hitting himself.

  "Big Hero! Don't shoot blindly!" Daoist Singularity floated over carefully, holding up an Eight Trigrams Shield. "Every mirror here is connected to a person's karma! Breaking them destroys someone's future!"

  Singularity looked at these mirrors, the data stream in his eyes spinning wildly.

  "These Prism Demons... they are using the refractive index of the mirrors to hide themselves."

  Slayer put away the shotgun.

  He switched to the BFG-9000. But he didn't fire that world-destroying green ball.

  He activated the BFG's [Scan Mode].

  A gentle green ripple spread out from the muzzle.

  The ripple swept across the surrounding mirrors.

  Ordinary mirrors had no reaction. But when the ripple swept across a few specific mirrors, the surfaces showed eerie distortions.

  "Found you."

  A cold sneer seemed to curl at the corner of Slayer's mouth.

  He didn't attack that mirror directly. He raised his right arm and activated the Shoulder Launcher.

  This time, he didn't load a grenade, but a Smoke Bomb.

  Poof!

  The smoke bomb exploded in the center of the maze. Thick white smoke instantly filled the gaps between the mirrors.

  Lasers need a medium to propagate, but the Prism Demon's invisibility requires the transmission of light.

  In the smoke, the originally invisible Prism Demons revealed faint outlines one by one—vacuums formed by their bodies displacing the smoke.

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  That was enough.

  Slayer drew the Crucible Blade.

  In the smoke, the red lightsaber was clearly visible.

  He charged in.

  Crack!

  Sword light flashed, and a Prism Demon hiding behind a mirror was sliced in half along with the mirror frame.

  Slayer's movements were terrifyingly precise. Every strike avoided the mirror surface itself, attacking only the demon entity hiding in the cracks between mirrors.

  One... two... ten...

  As the last Prism Demon turned into fragments, this layer finally quieted down.

  Daoist Singularity lowered his shield and rushed excitedly toward the mirrors.

  "Perfect! Too perfect!"

  Singularity took out a universal data cable (looking like a glowing tentacle) and plugged it directly into the interface of the largest main mirror.

  "Big Hero, look!"

  Singularity operated on his tablet.

  The countless mirrors that were originally playing random scenes suddenly changed pictures.

  They were no longer playing randomly but were integrated together to form a massive Surveillance Wall.

  [Access Point: Sky Eye System.]

  [Monitoring Range: All of Underworld + Key Areas of Mortal Realm.]

  [Functions: Facial Recognition, Real-Time Sin Analysis, Automatic Alarm.]

  "With this, I can see every corner of the Underworld from my office!" Singularity pointed at the ghosts eating roast chicken on the screen. "Who dares to urinate in public, who dares to fight, I'll know it all!"

  Slayer looked at this massive surveillance wall.

  His gaze didn't linger on those trivial scenes.

  He was looking for something.

  Soon, in the bottom right corner of the screen, he saw the image of the bottom of the Eighteenth Layer of Hell.

  There, directly below the large hole punched through, a blood-red door was trembling slightly.

  And in front of the door, a massive, blurry shadow seemed to sense the prying eyes and suddenly looked up at the "camera."

  Zzz—

  That screen instantly turned into static snow.

  Slayer withdrew his gaze.

  He knew that guy was already waiting for him.

  Singularity was still excitedly adjusting the camera angles: "Tilt that camera up a bit... yes, get a clear shot of Meng Po's Pavilion..."

  Slayer patted Singularity's shoulder.

  He pointed at their feet.

  Continue.

  "Privacy vs Security."

  In this Mirror Hell with no secrets, Slayer used smoke to force out the invisible enemies, while Singularity turned this omnipresent gaze into a Sky Eye guarding order.

  "Big Brother is watching you."

  This was no longer a terrifying prophecy, but a sign of improved security in the Underworld.

  "Next chapter, Fifth Layer: Steamer Hell. Slayer seemed to think it was too hot when he passed by just now? Maybe it's time to cool down the demons."