In the seventh episode of the original book, according to his self-description, we can know that the reason why he was demoted to a small demon from a general who commanded heaven in this mortal quicksand river was because he accidentally broke a glass, so he was knocked down in the quicksand river and suffered the pain of flying swords piercing his chest every day.
In heaven, there are strict rules and many rules. After all, no rule can make Fiona Fang do this. He must be punished so severely for doing something wrong. Some people say that it is because the cup is filled with nectar carefully prepared by the queen mother. Everyone knows that this kind of nectar is very rare and can improve the magic of immortals. So it is extremely important for the immortal who wants to be strong, but he accidentally knocked over the whole cup. Maybe it was very big, so it would make the jade emperor furious.
It is also said that at the flat peach meeting, Friar Sand threw a cup to vent his anger because he was dissatisfied with the small flat peach assigned to him. As we all know, the Flat Peach Conference is a grand banquet held by the Jade Emperor and the Empress Dowager, and flat peaches are very rare, and it will take hundreds of years to produce results, so everyone is graded according to their status. Friar Sand did nothing but hit the jade emperor in the face, which made him feel very angry, so he was right.