Chief of Staff to Klingon Chancellor Gorkon, Chang was a leader in the conspiracy to assassinate Gorkon, in order to obstruct peace initiatives between the Klingon Empire and the Federation.
In 2293, General Chang was part of the Klingon delegation aboard Kronos One, which was transporting Gorkon to Earth for historic peace talks. Chang came aboard the Enterprise-A, the Federation's escort ship, for a diplomatic dinner. Chang delighted meeting Captain Kirk, whom he regarded as a fellow "warrior." However, Chang later charged and arrested Kirk and Dr. McCoy for the murder of Gorkon, and successfully prosecuted them on the Klingon homeworld.
Chang put on a good show in the farcical trial, all along covering up his role in Gorkon's death from his Klingon colleagues, including the newly-installed chancellor - and Gorkon's daughter - Aztbur. Chang apparently arranged for a cloaked Bird-of-Prey to fire upon Kronos One - while cloaked - and knock out its gravity. This covert attack allowed two "hit men" to beam aboard from Enterprise and murder an off-guard Gorkon, effectively framing Kirk.
Chang was fond of quoting Shakespeare for virtually any occasion, especially aboard the prototype Bird-of-Prey during his final showdown with Kirk. When he realized that the Enterprise's torpedo could detect his ship's plasma signature and ultimately seal his fate, his final words were: "To be or not to be".