Chang was actually serving a fugitive tyrant from the 51st Century named Magnus Greel, the Minister of Justice for the Supreme Alliance of Eastern States, and Mr. Sin, a psychopathic pig cyborg.
Chang is in the service of Magnus Greel, a despot from the 51st century who had fled from the authorities in a time cabinet, now masquerading as the Chinese god Weng-Chiang. Afterwards, Chang had sent his men, including the diminutive Mr Sin, to kill Buller. 
