Where did the name "the coffin of the sky" come from?

Wang Jun, the director, explained the meaning of "The Sky", saying that "The Sky" is different from the general Qing Dynasty drama, and it is more like a TV series telling a fate story. "Pleiades" is one of the 28 stars, and it is said that it is a star of destiny. Those who are taken care of by the Pleiades usually have extraordinary abilities, sharp personalities and rich wealth. The Pleiades in the Sky revolves around the fates of Empress Dowager Cixi, Minister Liang Wenxiu and the little eunuch Chun Er.