"Hold on tight!" Ning Yu shouted to Mu Xue behind him, his voice echoing in the empty canyon.

Mu Xue stared intently at Ning Yu's movements, knowing that her life depended entirely on him. She imitated Ning Yu, taking a few steps back, taking a deep breath, and then leaping with all her might. However, her strength was ultimately inferior to Ning Yu's; her jump was too low, her fingertips barely brushing the protrusion before her body plummeted downwards.

"Ah!" Mu Xue exclaimed, her heart almost leaping out of her throat.

In a split second, Ning Yu reacted swiftly, grabbing Mu Xue's wrist. The immense pulling force made his arm muscles tense, almost dislocating them. He gritted his teeth, veins bulging in his arm, and used all his strength to pull Mu Xue upwards.

"Grab the bump!" Ning Yu roared, his voice hoarse from the effort.

Mu Xue's fingers trembled with fear, but she still managed to reach out and grab a protruding rock. The cold rock hurt her, but she dared not let go, for she knew that if she did, she would fall into the abyss.

Ning Yu gritted her teeth and pulled Mu Xue up little by little until she could firmly grasp the protrusion. Both of them were suspended in mid-air, their hands tightly clasped together, and they could feel the sweat and trembling in each other's palms.

"It's alright now," Ning Yu said, panting heavily.

Mu Xue took a few deep breaths to calm her wildly beating heart. She looked up at Ning Yu, her eyes filled with gratitude and lingering fear.

The two moved cautiously along the protrusions on the rock face. Every movement had to be precise; the slightest mistake would send them plummeting into the abyss. The wind whistled in their ears, and beneath their feet lay unfathomable darkness, a terrifying sight.

After a difficult climb, they finally reached the other side. The two collapsed to the ground, panting heavily, their bodies soaked in cold sweat.

“We… survived…” Mu Xue’s voice trembled slightly, filled with the relief of surviving a disaster.

Ning Yu nodded without speaking. He looked up and saw a massive stone gate standing before them, tightly closed, its surface carved with ancient and mysterious patterns. Beyond the gate lay a path leading to the unknown.

“This…” Ning Yu stood up, walked to the stone door, and reached out to touch the cold stone wall.

“It seems our journey is not over yet…” Mu Xue walked to Ning Yu’s side, looking at the tightly closed stone door, her voice low.

A chilling wind blew out from the crack in the stone door, carrying an unsettling aura. Ning Yu withdrew his hand from the stone door, turned to look at Mu Xue, and a resolute glint flashed in his eyes.

“Let’s go,” he said firmly.

Ning Yu and Mu Xue collapsed to the ground, panting heavily, overwhelmed by the exhaustion of surviving the ordeal. Sweat soaked through their clothes, clinging to their skin with a chill that contrasted sharply with the scorching post-nuclear-war air. The climb had nearly drained them of their strength, and the darkness below seemed ready to swallow everything; the fear of impending death still lingered in their minds.

"This godforsaken place..." Mu Xue cursed under her breath, rubbing her aching arms. She looked up ahead, where the massive stone gate stood like a silent giant, blocking their path.

Ning Yu slowly stood up and walked to the stone gate. The stone gate was cast from some unknown black metal, its surface smooth and cold, its touch like solidified night. Intricate patterns were carved upon it, resembling ancient script or mysterious symbols, appearing eerie and unpredictable in the dim light. He tried to push it, but the stone gate remained unmoved, as heavy as if it were one with the entire mountain.

“It seems brute force won’t work.” Ning Yu withdrew his hand, his brows furrowed. He walked around the stone door, carefully observing every detail, trying to find the mechanism or clue to open it.

Mu Xue also stood up and walked to Ning Yu's side. "The pattern on this door looks very strange," she said, pointing to the carvings on the stone door. "Doesn't it look like... a groove?"

Ning Yu looked in the direction Mu Xue was pointing, and sure enough, hidden among the complex patterns were some irregular grooves. These grooves were very shallow and difficult to spot without careful observation. They varied in shape and size, and were distributed in different locations on the stone gate, seemingly following some hidden pattern.

"It looks like some kind of key shape," Ning Yu mused. He reached out and touched the groove; the cold touch stirred something within him. He tried placing the several oddly shaped metal fragments he had previously acquired into the groove, but none of them fit.

“Could it be some kind of special stone?” Mu Xue suggested, looking around for clues. Scattered on the ground were pebbles of varying sizes and shapes. She bent down, picked up a stone that resembled one of the grooves, and tried to place it into it. The stone fit perfectly into the groove, making a soft “click” sound.

"Found it!" Mu Xue shouted excitedly.

A hint of joy flashed in Ning Yu's eyes. He continued searching for suitable stones around him and placing them one by one into the corresponding slots. As more and more slots were filled, the stone door began to vibrate slightly, emitting a low rumble. An ancient and mysterious aura emanated from the stone door, permeating the air and creating an inexplicable sense of oppression.

“Just one more piece…” Ning Yu looked around, but still couldn’t find a stone that matched the shape of the last groove. He felt a vague unease in his heart. The shape of this last groove was particularly complex, like a strange bird about to take flight, or a hideous and terrifying face.

“Ning Yu, look…” Mu Xue pointed to the bottom of the stone door, her voice trembling slightly. Ning Yu followed Mu Xue’s gaze and his expression changed abruptly.

Beneath the stone gate, a dark shadow was slowly wriggling...