In Ming dynasty, legend goes that there is an ancient deity's book covering a wide range of technical issues, including the unique method of manufacturing the weapons of deity, which has the power to destroy everything. He who gets that book rules the entire nation. Reportedly, in ancient times, deity made the royal family keep the book, as a sign of acknowledging their ruler-ship.
However, in Yuan dynasty, the Mongolians invaded the central plain and ruled the nation. There was chaos everywhere and the book which was supposed to be enshrined in the Imperial Palace was somehow missing and reappeared in the outlaw societies, luring lots of forces to fight for it.
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