The Returning Essence Secret Technique is a spell used to conceal one's cultivation level.
It has three layers; the first two are manageable, but the third involves creating a Small Void to hide spiritual power outside the body, in the heaven and earth.
This already resembles the Golden Core Domain of the Immortal Gate, except that the Returning Essence Secret Technique involves carrying a reservoir of spiritual power with oneself, which is rather limited in use.
Nevertheless, this Returning Essence Secret Technique must be of help to the Golden Core Domain, so Chen Mobai planned to send his little apprentice to find the source of this secret technique and seek out the specific cultivation method of the third layer.