Hanyuan Sword Cry

The young tombkeeper Lu Zhao is on duty at night and is attacked and killed by a mysterious man in black. A mysterious woman appears and frightens away the powerful enemy. What is the identity and motivation of the sword mark on the unknown monument and the man in black? Why would you attack a young man guarding the tomb of the Northern Army in the border town of Dayin Dynasty? What is the mystery of the young man's life experience?