Pei Yan
Meanwhile, Li Xian's relationship with Empress Wu was deteriorating, as Li Xian heard rumors that he was not born of Empress Wu but her sister Lady of Han, and was fearful. Meanwhile, earlier, Ming Chongyan (), a sorcerer trusted by Empress Wu and Emperor Gaozong, had repeatedly stated that he believed Li Xian did not have the abilities to be emperor, that his younger brother Li Zhe the Prince of Ying had an appearance like Emperor Taizong, and that another younger brother, Li Dan the Prince of Xiang, had the most honored appearance of all. Knowing that Li Xian was fearful of her, Empress Wu had the North Gate Scholars author teachings on filial piety to give to Li Xian, and also personally rebuked him, further causing him to be alarmed. When Ming was assassinated in 679, Empress Wu suspected Li Xian of carrying out the assassination. She had a report made to Emperor Gaozong that accused Li Xian of assassinating Ming. When the officials Xue Yuanchao, Pei Yan, and Gao Zhizhou were put in charge of investigations, they discovered a number of armors in Li Xian's palace. Empress Wu thus accused Li Xian of treason, and while Emperor Gaozong initially wanted to take no actions against Li Xian, at Empress Wu's insistence he relented. In fall 680, he reduced Li Xian to commoner rank, and created Li Zhe as the new crown prince.