Hidden Mountain on the Back of the Knife

An old knife that I got by chance has patterns of sixteen mountains carved on the back of the knife. A young man from a stable outside Yanmen Pass, carrying half a volume of incomprehensible silk books, walked into the frontier forty years of constant war between Song and Liao. He didn't know what mountain was carved on the knife. All he knew was that every time he practiced a style, there was an extra mountain on the back of the sword. On the day when the sixteen mountains are complete, it is time for Yanyun Sixteen Prefectures to return.