Legend has it that on a quiet night, when the moon is covered by dark clouds, the door of Wujiu's Tomb will open, and Wujiu Yuanying can come out. However, when the moonlight shines on the tombstone, the Yuanying will disappear and be locked up in the tomb again. Wu Jiu, the Lord of the Demon Prison, was imprisoned in the tomb by Immortal Emperor Jie Shuo and sealed with the Talisman of Zhi Yang because of his delusion to rule the three realms. After hundreds of years, Wujiu's Nascent Soul separated from the physical body and absorbed the demonic energy in the physical body to make itself stronger.