Heaven and earth have veins, human hearts have gu. At the beginning of antiquity, the nine luminaries ancestors observed the flow of mountains and rivers, knowing that greed, hatred, and ignorance can condense baleful energy, bury the earth's veins deeply, and manifest a thing named plunder gu. This thing has no fixed form, does not survive on flesh and blood, but feeds solely on the worldly attachments of people; if people pursue treasures, profits, or revenge, the slightest delusional thought in the depths of their heart becomes the nourishment for its growth. The ancestors cast blood seals into three parts, respectively suppressing the earth's veins of the north, south, and west, and also authored The Gu Classic, divided into upper and lower volumes. The upper volume records techniques of blending hundred herbs, while the lower volume writes of subduing plunder secrets, setting down the principle of 'symbiotic balance,' hoping that the living beings of rivers and lakes would each keep to their bounds and never face catastrophe. Alas, human hearts are difficult to restrain.