The Immortal Physician's Transmigration: Miraculous Rejuvenation

After defeating the dark behemoth, Ye Yuanchen and the others continued deeper into the mysterious space, following the faint spiritual energy pathways. The surrounding darkness seemed to come alive, constantly twisting and writhing, as if resisting their progress.

"Everyone, cheer up! I feel we're getting closer and closer to the truth." Ye Yuanchen's gaze was firm, and the Lingxu Holy Sword in his hand shimmered with a faint light, illuminating a small area in front of everyone.

Mu Wanyue nodded gently, her hand gripping the Spirit Whip tightly, its pink blade contrasting sharply with the surrounding darkness. "I hope all of this can end soon. The Spirit Realm and the Three Realms have already suffered too much."

Lu Zixuan, meanwhile, vigilantly observed his surroundings, his hands ready to set up new formations at any moment to deal with any potential dangers. "This mysterious space is full of eeriness; we cannot let our guard down."

Bai Youruo played the Lingxu Lingyin Flute, the sound echoing in the darkness. Although it could not completely dispel the darkness, it could keep everyone's minds clear and prevent their souls from being eroded by the endless darkness.

As they ventured deeper, a massive, dark castle came into view. Its walls soared into the clouds, emanating a thick aura of darkness. The walls were covered with strange runes and patterns, which shimmered with a chilling light, as if telling ancient and sinister tales.

“This castle looks like the core of the dark forces. We need to be careful,” Ye Yuanchen said, slowing his pace and cautiously approaching the castle.

When they arrived at the castle gate, they found it tightly shut, with a huge black gem embedded in it, and something seemed to be surging within the gem. Ye Yuanchen tried to push the gate open with his spiritual power, but the gate did not budge.

"This door seems to be sealed by a powerful restriction; we need to find a way to break it." Lu Zixuan stepped forward and carefully studied the restriction on the door.

Mu Wanyue swung her Spirit Whip, which struck the gate, sending up a shower of black sparks, but the gate remained tightly shut. "This restriction is so strong, my attacks are completely ineffective."

Bai Youruo stopped playing the flute, closed her eyes, and focused her mind on sensing the restriction on the gate. After a moment, she opened her eyes and said, "This restriction seems to be related to an ancient dark pact, which requires specific power to break."

After a moment's thought, Ye Yuanchen said, "Could it be related to the Key to the Spirit Realm? We've already used it to defeat the Dark Beast; perhaps it can also unlock the seal on this gate."

He took out the Spirit Key again and brought it close to the black gem on the door. As soon as the Spirit Key approached, the black gem began to tremble violently, and the runes on the door flickered even more frequently. Suddenly, a beam of black light shot out from the gem and struck the Spirit Key. The Spirit Key shone brightly, resisting the black light.

After a dazzling flash of light, the door slowly opened, and a powerful dark force rushed out. Ye Yuanchen and the others hurriedly activated their spiritual energy shields to resist the impact of this dark force.

Stepping into the castle, it was dark and damp, filled with a putrid stench. The hall was filled with strange objects and statues, their distorted and bizarre appearances sending chills down one's spine.

“The truth about the dark forces must be hidden here. Let’s search carefully,” Ye Yuanchen said, and he began to look around the hall.

At the far end of the hall, they discovered a huge black book. The book hovered in the air, emanating a strong aura of darkness. Ye Yuanchen cautiously approached the black book; he could sense that it contained a great secret.

The moment his hand touched the book, a powerful surge of information flooded his mind. It turned out that this black book was the origin book of dark forces, recording the process and purpose of their birth.

Long, long ago, at the dawn of creation, the Spirit Realm, the Cultivation Realm, and the Mortal Realm were a harmonious and coexisting whole. However, a dark energy from the depths of the universe invaded this world. This dark energy merged with the negative emotions and desires within, gradually forming a dark force. The purpose of this dark force was to shatter the balance of the three realms, dragging the entire world into an endless abyss of darkness, allowing darkness to reign supreme over everything.

The remnants of dark demonic gods, dark creatures, and various dark phenomena they encountered were all means released by the dark forces to achieve their goals. The spirit realm became the breakthrough point for the dark forces because it is the spiritual energy hub connecting the three realms. Once the spirit realm is controlled by the dark forces, the balance between the three realms will be completely broken, and the dark forces can easily spread to the entire world.

“I see. We must stop the dark forces’ conspiracy,” Ye Yuanchen said, his eyes revealing a firm resolve.

Mu Wanyue frowned and said, "But what should we do? The dark power is so strong that simply sealing it doesn't seem to solve the problem completely."

Lu Zixuan pondered for a moment and said, "According to the records in this book, to completely eliminate the dark forces, we need to find the Heart of the Three Realms. The Heart of the Three Realms is the core power of the Three Realms. Only by fusing the power of the Heart of the Three Realms with the power of the Key of the Spirit Realm can we create a purifying light that is enough to destroy the dark forces."

Bai Youruo played the Lingxu Lingyin Flute, her melody tinged with worry. "But where is the Heart of the Three Realms? This is another difficult problem."

Ye Yuanchen looked at the black book and said, "This book might contain clues about the location of the Heart of the Three Realms. Let's study it more carefully."

They began to carefully read the contents of the black book, searching for clues about the location of the Heart of the Three Realms. After some effort, they finally found a vague record in the corner of the book: "The Heart of the Three Realms is located at the intersection of the Three Realms, hidden in the turbulent currents of spacetime, and can only be touched by pure spirits and fearless hearts."

"The intersection of the three realms? A spacetime turbulence? That sounds very dangerous," Mu Wanyue said.

Ye Yuanchen took a deep breath and said, "No matter how dangerous it is, we have to try. For the peace and tranquility of the Three Realms, we cannot back down."

Having reached a consensus, the group decided to leave the Dark Castle and head to the intersection of the Three Realms to find the Heart of the Three Realms. They knew that even more difficult and dangerous challenges awaited them, but they had no way back. To completely destroy the dark forces and save the Three Realms, they were willing to pay any price.