Many heaven flames were bound under rules of Nature. They were brought into a mysterious, unknown area together with the Immemorial Demonic Flame. Nobody could enter or sense the mysteries of this place.
Shi Yan had a soul connection with the heaven flames so he could use the heaven flame's soul energy fluctuation to sense that something strange was happening in that place, something that the naked eye couldn't see. He could use his Soul Consciousness to grab something for a while...
Earth and heaven energy in that place was strange and had clear movement. It seemed that if a warrior cultivated there, he would simply receive the true meanings of a power Upanishad.
In that place, powers Upanishad could explain themselves in magical ways. If the soul of a warrior could get in there, that warrior could use this method to explain their powers and study further. He would eventually reach a profound level of understanding his power Upanishad.