Gaozong and Empress Wu, exceedingly powerful, and he grew particularly corrupt. In 663, after reports of Li Yifu's corruption were made to Emperor Gaozong, Emperor Gaozong had Liu Xiangdao and Li Ji investigate, finding Li Yifu guilty. Li Yifu was removed from his post and exiled, and would never return to Chang'an. During the years, Empress Wu had repeatedly, in her dreams, seen Empress Wang and Consort Xiao, in the states they were after their terrible deaths, and she came to believe that their spirits were after her. For that reason, Emperor Gaozong started remodeling a secondary palace, Daming Palace (), into Penglai Palace (), and when Penglai Palace's main hall, Hanyuan Hall (), was completed in 663, Emperor Gaozong and Empress Wu moved to the newly remodeled palace (which was itself later renamed to Hanyuan Palace). (However, Empress Wang and Consort Xiao continued to appear in her dreams even after this, and therefore, late in Emperor Gaozong's reign, he and Empress Wu were often at the eastern capital Luoyang, not at Chang'an.) Also in 663, the Tibetan Empire attacked a Tang vassal state, the Tuyuhun. Tuyuhun's Ledou Khan Murong Nuohebo, unable to withstand the Tibetan attack, took his people and fled into Tang territory to seek protection, thus ending Tuyuhun's existence as a state. Meanwhile, also in 663, Liu Rengui and Liu Renyuan, in conjunction with Munmu of Silla and the former Baekje crown prince Buyeo Yung, defeated Buyeo Pung and Japanese forces sent to assist him, at the Battle of Baekgang. Buyeo Pung fled to Goguryeo, ending the Baekje resistance movement. Emperor Gaozong recalled Liu Renyuan, leading Liu Rengui in charge of former Baekje territory, but in 664 sent Liu Renyuan back to Baekje and tried to recall Liu Rengui. Liu Rengui petitioned to remain to prepare for another attack on Goguryeo, and Emperor Gaozong agreed to let him remain. By 664, Empress Wu, who felt that her power was well established, was extending her influence further in the political arena and increases her controlling behavior over Emperor Gaozong and arbitrarily makes many government decisions. According to Song dynasty historian Sima Guang in the Zizhi Tongjian: In the same year when the eunuch Wang Fusheng () reported to Emperor Gaozong that she had engaged the sorcerer Guo Xingzhen () – an act that was strictly forbidden—Emperor Gaozong, in anger, summoned the chancellor Shangguan Yi to consult Shangguan. Shangguan