Ling Yun is an inconspicuous outer disciple of the Qingyun Sect, with mediocre spiritual qualifications and is still stuck on the second level of Qi Refining after three years of practice. Su Muxue is an apprentice in the alchemy room. Although she is proficient in identifying medicines, she has no talent for cultivating immortals and can only live with medicinal herbs all day long.
During a sect mission, the two accidentally fell into the "Secret Realm of the Fallen Immortal" deep in the mountains. The spiritual energy in the secret realm was disordered and strange beasts were rampant. Just when they were in a desperate situation, they unexpectedly met the ancient immortal master Mo Yuan who had been sleeping for thousands of years in the "Immortal Master Palace" deep in the secret realm.
Mo Yuan sensed the "Mutated Thunder Spirit Root" hidden in Ling Yun's body and Su Muxue's "Innate Medicine Soul", and made an exception to accept the two as disciples. He taught Ling Yun the "Thunder God Art" to help her awaken the power of the Thunder Spirit Root. He also gave Su Muxue the "Ten Thousand Medicines Classic" to master the supreme method of identifying medicine and refining elixirs.
However, the secrets of the secret realm go far beyond that. As the two people improve their cultivation, they discover that there is a "spirit-eating giant beast" sealed at the bottom of the secret realm, and disciples of the cult "Netherworld Pavilion" have sneaked in, trying to seize the inheritance of the immortal master and release the giant beast.
In order to protect the secret realm and inheritance, Ling Yun used the power of thunder spirit roots to fight against the evil cultivators of Netherworld Pavilion. Su Muxue refined the "Evil-Breaking Pill" based on the "Ten Thousand Medicines Sutra" to assist in the battle. The two went through the test of life and death in the secret realm. Not only did their strength improve rapidly, they also revealed the shocking secret of the immortal master's sleep and the seal of the giant beast, and finally became the new guardians of the secret realm.
