Why did Marshal Tianpeng cast a pig fetus?

According to the legend of Taoism, during the dragon and Han Dynasties, there was a king named Tongyu. The king had a jade imperial concubine named Mrs. Ziguang, who gave birth to nine sons. The second eldest son was Emperor and Ziwei emperor, and the other seven sons were the Big Dipper. Therefore, Mrs. Ziwei was also called Doumu Yuanjun. One of the sons is named Tianpeng Xingjun. He is dignified and majestic. He is a pig. We all know the following story. The Supreme Lord specially asked him to take charge of the divine army. Later, when the jade emperor ascended the throne, he was entrusted with an important task. He hired him as the Grand Marshal of the 360000 water army, still using the name of the canopy, so he was called Marshal Tianpeng, and then Gong Dou opera, which took place between the Jade Emperor, Ziwei emperor, marshal Tianpeng and Chang‘e fairy. So tianpengmeng flirted with Chang‘e‘s injustice and was demoted to the world, so he cast a pig fetus. On earth, the emperor regarded himself as the Jade Emperor on earth, so the Dragon Robe was purple, and the palace city was called the Forbidden City.

There are several versions of the Big Dipper, one of which is directly related to our Feng Shui.