For Su Yang to use the Secret Technique of Devouring the World, he had to use the power of the Heaven Slayer, which meant the power of demons.
However, that demonic power within him existed inside the Undying Bone.
When this power left the Undying Bone and flowed into his flesh and meridians, it ran into an accident Su Yang had never anticipated.
This Demon Power, upon encountering the Undying Golden Body, actually clashed with the Buddha Power contained within the Undying Golden Body. The two powers canceled each other out inside Su Yang's body, causing him to be completely unable to use the Demon Power, and thus unable to unleash the Secret Technique of Devouring the World.
Things had become awkward at this point. All these years, Su Yang had mainly cultivated the Heaven Slayer's Secret Techniques, which were all Demon Power.
