What are the interesting details of the movie The Painted King of Yin and Yang?

The "King of Yin and Yang" in the film is a "four unlike" who is neither a man nor a ghost, nor a god nor a demon, nor a yin nor a yang, and has been practicing for thousands of years. Because it has nothing to do with all walks of life, no god can manage it. As a result, he controlled a group of ghosts who went to the underworld to reincarnate, became kings on their own, and became arrogant. The interesting thing in the movie is its dialogue with Sun Desheng, a sly old ghost. When the "King of Yin and Yang" appeared, all the ghosts sang in unison: "King of Yin and Yang, long live without borders, like parents". Hehe, this passage, like Jin Yong's novels, is meaningful if it is related to a certain period of history.