Wang Mang
Circa 5 AD, Emperor Ping, having grown older, appeared to have grown out of his earlier heart condition, and it became fairly plain that he resented Wang Mang for slaughtering his uncles and not allowing his mother to visit him in Chang'an. Wang Mang therefore resolved to murder the emperor. In winter 5 AD, Wang Mang submitted pepper wine (considered in those days to be capable of chasing away evil spirits) to the 13-year-old emperor, but had the wine spiked with poison. As the emperor was suffering the effects of the poison, Wang Mang wrote a secret petition to the gods, in which he offered to substitute his life for Emperor Ping's, and then had the petition locked away. (Historians generally believed that Wang Mang had two motives in doing this—one was, in case Emperor Ping recovered from the poisoning, to use this to try to absolve himself of involvement in the poisoning, and the second was to leave for posterity evidence of his faithfulness.) After a few days of suffering, Emperor Ping died. The throne would lie vacant for the next few years, as although Emperor Ping's cousin-once-removed, the infant Emperor Ruzi, would be selected as emperor, he would never actually take the throne. Wang Mang would serve as acting emperor and usurp the Han throne officially in 8 AD.