Genshin Impact.

Lin Feng and Li Er, led by the old man, came to a mysterious valley. The valley was shrouded in mist, and the surrounding mountains towered into the clouds, giving people a mysterious and solemn feeling.

"This is the starting point of your tribulation." The old man put his hands behind his back and looked ahead with deep eyes.

Lin Feng's eyes were firm, and he bowed and said, "Thank you for your guidance, senior. Li'er and I will do our best." Li'er also nodded slightly, with anticipation and determination flashing in her eyes.

The old man raised his hand gently, and a beam of light flew out of his hand and disappeared into the valley. Then, a small path with a faint light appeared in the valley. "Follow this path, and the immortal will appear. As for whether you can understand the mystery, it depends on your own luck."

Lin Feng and Li'er looked at each other and then set foot on this immortal road. The path was winding, and the flowers, plants and trees on both sides emitted strange light, as if telling ancient secrets.

After walking for a while, they came to a lake. The water was so clear that the stones and water plants on the bottom of the lake were clearly visible. However, the lake was covered with a layer of light mist, making it difficult to see clearly.

"Brother Feng, this lake is so strange." Li'er said softly.

Lin Feng frowned and approached the lake cautiously. At this moment, ripples suddenly appeared in the lake, and a huge figure slowly rose from the bottom of the lake.

It was a huge water beast, covered with blue scales, with fierce eyes. The beast opened its bloody mouth and pounced towards Lin Feng and Li'er.

Lin Feng and Li'er reacted quickly. Lin Feng drew out his sword and performed a set of sharp sword techniques. The sword shadow flashed and attacked the water beast. Li'er formed seals with both hands and cast a spell. Rays of light flew towards the water beast.

The water beast was very powerful and had a fierce battle with Lin Feng and Li'er. Although Lin Feng's swordsmanship was exquisite, the scales of the water beast were extremely hard, and the sword could only splash sparks when it was cut. Li'er's magic could only cause slight damage to the water beast.

During the battle, Lin Feng gradually discovered that the water beast's attacks seemed to have a certain pattern. While dealing with the water beast, he carefully observed its movements. Finally, he found the water beast's flaw.

"Lier, cooperate with me!" Lin Feng shouted.

Li Er understood what he meant and cast a spell again to restrain the water beast's movements. Lin Feng took the opportunity to fly up and pierce the water beast's eyes with the sword in his hand. The water beast was unable to dodge and was stabbed by Lin Feng's sword.

The water beast screamed and fell into the lake, creating huge waves. Lin Feng and Li'er breathed a sigh of relief, but before they could recover, a whirlpool suddenly appeared on the lake.

The vortex spun faster and faster, sucking Lin Feng and Li'er in. They only felt their eyes go dark before they lost consciousness.

After an unknown amount of time, Lin Feng slowly opened his eyes and found himself in an unfamiliar cave. There was a pungent smell in the cave, and strange lights flickered on the walls.

"Li'er, Li'er!" Lin Feng shouted loudly.

"Brother Feng, I'm here." Li'er's voice came from a distance.

Lin Feng walked in the direction of the sound and finally found Li'er. At this time, Li'er was trapped in a huge light shield and could not move.

"Brother Feng, please save me quickly." Li'er said anxiously.

Lin Feng tried to break the light shield, but no matter how he attacked, the light shield did not move at all. Just when he was at a loss, a low laugh suddenly came from the cave.

"Haha, do you think it's so easy to pass the test?" said a mysterious voice.

Lin Feng looked around and asked loudly: "Who are you? Why are you making things difficult for us?"

"I am the guardian of this immortal road. If you want to pass through here, you must solve the puzzle here." said the mysterious voice.

Lin Feng looked at the light shield, thinking about how to crack it. Suddenly, he found some strange runes engraved on the light shield. He studied these runes carefully and found that they seemed to be an ancient code.

After some effort, Lin Feng finally cracked the code of the rune, the light shield slowly disappeared, and Li'er was saved.

"Brother Feng, you are so awesome." Li'er threw herself into Lin Feng's arms.

Lin Feng smiled and said, "We can't let our guard down yet. There will definitely be more tests waiting for us on this path to immortality."

The two continued to move forward, encountering various traps and powerful monsters along the way, but with their mutual cooperation and efforts, they resolved them one by one.

Finally, they came to an ancient palace. The door of the palace was closed, and some mysterious patterns were carved on the door.

"This should be the place where the immortal secret lies." Lin Feng said.

Li'er nodded, and the two walked forward and gently pushed open the palace door. Inside the door, a ray of light flickered, and the secret of the fairy machine was about to be revealed...