When they received the news of the Sect Leader Succession Ceremony, Yu Xian and Yue Jiu were studying the recently acquired secret technique- "Internal Devil".
This technique harmonizes both the Daoist and demonic, connecting heaven and earth, incorporating Yin and Yang. Its main focus is how to use the method of dual cultivation to fuse the Yin and Yang energies of heaven and earth, simulating the process of nurturing a Daoist Seed within the Daoist Body, and eventually cultivating an alternative demonic seed within one's body.
However, since it's only a semi-finished technique.
Though the description of the dual cultivation process is quite rich, the details on how to cultivate the demonic seed are vague, significantly diminishing its value.
Without the latter part, no one knows what kind of monster will eventually be bred from it.
With the belief in the rigor of practical knowledge.