Qimen Dunjia was a type of divination in ancient China. It originated in the Tang Dynasty and mainly studied how to use the characteristics of time and space to predict the future. The specific content of Qimen Dunjia included divination, astrolabe deduction, talisman sacrifice, and other aspects. It was regarded as one of the peaks of ancient Chinese divination. In novels, Qimen Dunjia was often described as a mysterious power that could control fate and fortune through the power of time and space. In some novels, Qimen Dunjia was used to predict war, wealth, fate of characters, and so on. Therefore, it was often used as the background and key element of the story.