Emperor Gaozong died in 683, and was initially succeeded by his and Empress Wu's son
Li Zhe the
Crown Prince (as Emperor Zhongzong), but Empress Wu retained power as
empress dowager and
regent. In spring 684, after Emperor Zhongzong showed signs of independence, she deposed him and replaced him with another son,
Li Dan the Prince of Yu, but wielded power even more tightly thereafter. Around this time, it appeared that Wu Chengsi became a close confidant of hers, and later that year, when the
chancellor Liu Rengui, who was then in charge of the capital
Chang'an (with Empress Dowager Wu, who disliked Chang'an and favored the eastern capital
Luoyang, taking up permanent residence at Luoyang), offered to resign, it was Wu Chengsi that she sent to Chang'an to comfort Liu and to dissuade him from resigning. It was also Wu Chengsi who formally acted for her at Emperor Ruizong's enthronement. In summer 684, she made Wu Chengsi the minister of rites and gave him the designation
Tong Zhongshu Menxia Sanpin (), making him a chancellor
de facto, although she removed him from that position three months later and made him the minister of ceremonies. Later that year, pursuant to a formal request of his, she posthumously created five generations of Wu ancestors princes or dukes and built a five-generation ancestral temple for them, second only to the imperial ancestral temple (which included seven generations). Meanwhile, he and a cousin,
Wu Sansi (Wu Yuanqing's son), knowing that Empress Dowager Wu was contemplating taking the throne herself, advocated that two senior members of the Li imperial clan—Emperor Gaozong's uncles Li Yuanjia () the Prince of Han and Li Lingkui () the Prince of Lu—be killed, lest that they interfere with her plans. Empress Dowager Wu agreed, but did not immediately carry out the plan. In 685, Empress Dowager Wu made Wu Chengsi chancellor again (this time with the modified designation
Tong Fengge Luantai Sanpin (), as she had changed many office names in the government structure) but removed him a month later. In 686, fearful of the general Li Xiaoyi () -- a member of the imperial Li clan who had defeated the anti-Empress Dowager Wu rebellion led by
Li Jingye the Duke of Ying in 684—Wu Chengsi made false accusations against him, and in response, Empress Dowager Wu demoted Li Xiaoyi. In 687, Wu Chengsi further accused Li Xiaoyi of having made comments that he would be emperor one day, and Empress Dowager Wu had Li Xiaoyi exiled to Dan Prefecture (, modern
Danzhou,
Hainan), where he died in exile. In 688, Wu Chengsi had the words, "The holy mother is on earth, and the imperial sovereignty will forever be magnified" () carved onto a rock and then had the rock thrown into the Luo River (, near Luoyang). He then had the commoner Tang Tongtai () "discover" the rock and offer it to Empress Dowager Wu as a sign of divine favor. Empress Dowager Wu was very pleased and claimed herself the honorific title, "Holy Mother, the Divine and August One" () and set a date to offer sacrifices to the god of Luo River, ordering the commandants, prefects, and nobles to be gathered at Luoyang for the sacrifices. This caused the Li clan imperial princes to be fearful that she was intending to slaughter them, and in response, Emperor Gaozong's brother
Li Zhen the Prince of Yue and Li Zhen's son
Li Chong the Prince of Langye rose in rebellion against her, but both were quickly defeated; Li Chong was killed in battle, while Li Zhen committed suicide. Empress Wu took this opportunity to have her trusted secret police official
Zhou Xing arrest Li Yuanjia, Li Lingkui, Li Yuanjia's son Li Zhuan () the Duke of Huang, Emperor Gaozong's aunt Princess Changle, and Princess Changle's husband Zhao Gui () and force them to commit suicide. Subsequently, another uncle of Emperor Gaozong, Li Yuangui () the Prince of Huo, was exiled, and died on the way to exile; his son Li Xu () the Prince of Jiangdu and a cousin of Emperor Gaozong's, Li Rong () the Duke off Dongwan, were executed. In 689, Empress Dowager made Wu Chengsi
Nayan () -- the head of examination bureau of government and a post considered one for a chancellor. In 690, she made him
Wenchang Zuo Xiang () -- one of the heads of the executive bureau of government, also considered a post for a chancellor. Around the same time, he had Zhou falsely accuse Emperor Gaozong's sons by other consorts,
Li Shangjin () the Prince of Ze and
Li Sujie the prince of Xu, of treason. Empress Dowager Wu summoned Li Shangjin and Li Sujie to Luoyang and had Li Sujie strangled; Li Shangjin committed suicide. Later that year, Emperor Ruizong yielded the throne to Empress Dowager Wu. She took the throne as "emperor" and established her Zhou dynasty, interrupting Tang. She had a number of her Wu relatives created imperial princes, and Wu Chengsi was created the Prince of Wei. == During Wu Zetian's reign ==