The blue light seeping from the crack grew brighter and brighter, as if something underground was breathing. Chen Hao stared at the crack, feeling a slight vibration beneath his feet—not fast, but steady, like a heartbeat.

He raised his hand and touched his left arm—it had scraped against the rock wall during his sprint, and it burned with pain, but he could still move it.

“Don’t just stand there,” he said. “It’s opened a crack, which means we haven’t gone the wrong way.”

Susan stood diagonally behind him, holding the protective bag. The crystal was still glowing, its rhythm much more precise than before, alternating between light and darkness, as if responding to something.

The green light on Nana's right arm flickered, and the system notifications came on and off. She didn't speak, but simply pointed the guide stick forward.

Carl leaned against the wall, the scorch marks on his right hand still smelling of smoke. He looked down at his toolbox, pulled out a cooling pad, stuck it on his arm, and frowned.

“This place is more annoying than my mom’s nagging,” he said.

No one laughed, but the atmosphere relaxed a little.

The four regrouped, with Chen Hao in front, Susan in the middle, Carl at the rear, and Nana on the outermost edge. They moved forward along the left rock wall, their steps light, testing the waters before each step.

The passage narrowed, and the overhead rocks pressed down, forcing you to duck every few steps. The ground was no longer gravel, but a smooth slab of black stone, which was a bit slippery underfoot.

Blue light seeped out from the cracks, shining on the wall and revealing strange patterns. These patterns weren't carved; they seemed to grow out of the wall, moving and flowing slowly, like blood vessels.

“It’s alive,” Susan whispered.

“Who?” Carl asked.

"This wall."

Chen Hao stopped and reached out to touch the wall. It was cold, but he could feel something moving inside. He withdrew his hand and shook his fingers.

“Stop touching me,” he said. “We’re here to do business, not to make friends.”

The ground shook violently as soon as he finished speaking.

It wasn't the previous three short and two long beats; this time it was a continuous tremor, getting faster and faster, like drumbeats.

The patterns on the rock wall suddenly lit up, and the blue light spread rapidly, covering the entire passage in the blink of an eye. The circular outline ahead began to glow, and concentric rings appeared on its surface, as if a lock had been opened.

“It knew we were coming,” Nana said.

Her voice was a little choked up; the system was overloaded, and her speech became mechanical.

“Then let’s make an appearance.” Chen Hao took a step forward. “We can’t expect it to invite us for tea.”

They continued forward, fifteen meters, ten meters, five meters.

Suddenly, several thin cracks appeared in the paving stones in front of the round gate, from which blue light shot out, forming a curtain of light. The air began to distort, and the temperature soared.

"Retreat?" Karl asked.

“It’s too late.” Susan clutched the protective bag tightly. “It’s already activated.”

A crack slowly opened in the center of the light screen, like a door being pushed open. A dark figure slowly moved out from inside.

The creature had six legs, their joints bending in a way unlike those of Earth creatures; with each step, the ground would dent slightly. Its body was covered in a crystalline shell that gleamed metallically under blue light. Its head had no nose or mouth, only two reddish light sources, like molten iron.

When it's still, it looks like a sculpture. But it moved.

The first step is to lift your leg.

The second thing is to turn towards them.

On the third strike, both red eyes went out for a brief moment.

In that instant, an invisible force swept through the passage. Karl collapsed to his knees, clutching his head and retching. Susan staggered backward, a trickle of blood running down her ear. Sparks flew from Nana's right arm, and she swayed before regaining her balance.

"Shield!" Chen Hao shouted.

Nana immediately raised her left shoulder, and a semi-transparent barrier unfolded, enveloping the four of them. The shockwave struck it, producing a dull thud, like someone smashing glass with a hammer.

“It won’t last long,” she said. “The energy will only last for thirty seconds.”

"That's enough." Chen Hao stared at the creature. "It will blink before it attacks; that's when it's charging up."

"You mean...it has a delay?" Susan wiped the blood from her ear.

"Yes. Just like changing channels on an old TV, you have to wait a while before the picture appears."

"So we have to move while it's 'black screen'?"

"clever."

"Then you take command."

Chen Hao took a deep breath: "Wait for the lights to go out again, everyone step three steps to the left, don't look back, don't stop."

They had just gotten into position when the creature's red eyes went out once again.

"Let's go!" Chen Hao roared.

The four of them moved to the left at the same time. Almost simultaneously, a burst of blue flame exploded where they had just been standing, and the stone instantly vaporized.

“It works!” Carl gasped.

"Don't be too happy yet." Chen Hao looked ahead.

The creature turned around, moving twice as fast as before. It didn't approach again, but instead raised a leg and gently tapped the ground.

Three electric arcs separated from it, slithering through the air like snakes, encircling it from three directions.

"Disperse!" Chen Hao shouted.

Susan rolled to the right, clutching the protective bag; Carl lunged towards the left corner; and Nana dragged her right arm behind a stone pillar. Chen Hao pressed himself against the wall, his heart pounding as if it would burst from his throat.

The electric arc followed the ground, exploding into sparks upon hitting the rock face. One of the arcs grazed Susan's backpack, burning through the fabric instantly.

"My new bag!" she cursed.

"Save your energy," Carl said, lying on the ground. "You can complain when you get back alive."

Nana leaned against the stone pillar, her right arm indicator light turned red, and the system interface displayed only one line of text: **Basic voice output is in progress**.

She looked up at the creature, then looked down at the guide stick in her hand.

“Frequency…” she murmured, “It’s synchronized with the crystal…”

Upon hearing this, Chen Hao abruptly looked up: "What did you say?"

“Its rhythm of action…is consistent with the main crystal,” Nana said haltingly. “It might be controlled by a homologous signal.”

“So that means…” Chen Hao looked at Susan, “we can interfere with it using crystals?”

“The risk is huge,” Carl said. “Once the light source is exposed, it could lock onto us directly.”

"Which step isn't risky now?" Chen Hao looked at Susan. "Do you dare?"

Susan didn't speak, but looked down at the protective bag in her arms. The crystal was flashing violently, as if it had sensed something.

She unzipped the zipper and took out the crystal.

The blue light instantly illuminated the entire passageway.

The creature's movements changed immediately. It stopped all movement, its six legs slightly bent, and its red eyes, fixed on the crystal, ceased to flicker.

“It’s looking,” Nana said. “It recognizes this.”

“It’s not just that it recognizes it.” Chen Hao narrowed his eyes. “It’s afraid of this.”

He slowly stood up, walked to Susan's side, and reached out to touch the surface of the crystal. It was warm, and the frequency of its pulsation was exactly the same as the ground's vibrations just now.

“It’s the gatekeeper,” he said, “but this is the key.”

The creature suddenly moved. Instead of attacking, it took a step back, then raised its forelimbs, making a "blocking" gesture.

“They won’t let us in,” Susan said.

“But it didn’t attack.” Chen Hao laughed. “That means it knows the rules—the person with the key can’t be killed.”

"Shall we charge in?" Carl asked.

“No,” Nana said. “There’s a door behind it; forcing our way through will trigger a chain reaction.”

"So we'll just wait it out?" Susan frowned.

“No.” Chen Hao placed his hand on the crystal. “We’ll give it a command.”

How should I give it to you?

"Slap the ground."

He squatted down and slapped the ground hard with his palm.

Three short strokes, two long strokes.

pause.

repeat.

It was the same rhythm they used when they crossed the barrier.

The creature's red eyes flashed, and its movements paused briefly.

“It works!” Karl whispered.

Chen Hao continued filming, maintaining a steady pace. After each take, the creature's body would tremble slightly, as if receiving a signal.

Nana immediately retrieved the residual data and compared the crystal frequency with the biological reaction time.

“It is influenced by rhythm,” she said. “If we can match the resonance point, it may be possible to temporarily cause it to lose its uncontrolled behavior pattern.”

“Then increase the signal.” Chen Hao looked at Karl. “How much capacitor do you have left?”

Carl pulled out two spare batteries: "Enough for one strong pulse."

“Connect the crystal,” Chen Hao said. “Let’s have a big sing-along.”

Carl quickly modified the wiring, connecting the battery to the interface on the protective bag. Susan gripped the crystal, ready to unleash the light at any moment.

Nana leaned against the stone pillar, her voice growing weaker and weaker: "Countdown... three seconds... synchronized activation..."

Chen Hao raised his hand.

Carl pressed the switch.

Susan opened the protective bag.

The three acted simultaneously.

Blue light bursts forth.

Slap the ground with your palm.

Current injection.

The creature's red eyes suddenly contracted, and all six legs stiffened simultaneously. Its shell began to crackle, as if its internal structure was dislocating.

It wanted to move, but couldn't.

It wanted to attack, but its rhythm was disrupted.

Chen Hao, panting, watched as the guy gradually lost his balance.

“It seems,” he said, “that you are not invincible after all.”

The creature finally gave way, collapsing to its knees on one leg, then the other. It tried to stand, but as the third thud sounded, its entire body swayed and lurched heavily to one side.

At the end of the passage, only its heavy breathing could be heard.

Chen Hao turned around and looked at the three of them.

“The door is still there,” he said. “We still have a chance.”

Susan held the crystal, her hands still trembling.

Carl was dismantling the wires, looking exhausted.

Nana leaned against the stone pillar, the red light on her right arm flashing continuously, and uttered her last complete sentence:

"Fifteen meters from the entrance."

Chen Hao took a step.

A sliver of blue light seeped out from the crack in the ground.