Even the methods of refining Ghost Path Dharma Instruments and Spirit Pills are discussed in it.
Among them is a Soul Path Secret Technique called the "True Spirit Immortality Mantra," which strengthens the true spirit consciousness of Ghost Cultivators, preventing the loss of true self-awareness over long years and the erosion by the Energy of Yin Fiend.
Nascent Soul Stage Cultivators, due to the uniqueness of the Nascent Soul, can also practice this technique to strengthen their true self-awareness, enhance resistance to fascination divine skills, and prevent themselves from being soul-searched.
The Mystic Fiend True Person likely practiced this Soul Path Secret Technique in their lifetime, which allowed their true spirit to endure after their fall, persisting to this day.
Of course, it's more likely that after their death, they prepared to convert to Ghost Cultivation, but couldn't completely succeed, only gaining some Ghost Cultivation characteristics.
