General Chang was a Klingon officer and chief of staff to Gorkon, Chancellor of the Klingon High Council in 2293. In that year, Chang was involved in the conspiracy to sabotage peace talks between the Klingon Empire and the United Federation of Planets.
Chang was extremely fond of Shakespeare, and often quoted lines from his various plays. Chancellor Gorkon rakishly presumes one has to enjoy Hamlet in the original Klingon, a possible hint why Chang repeatedly utilizes Shakespearean quotes.
In an attempt to frame Captain James T. Kirk for the assassination of Chancellor Gorkon, Chang commanded an experimental Klingon Bird-of-Prey which had the unique ability to fire its weapons while under cloak. Chang's ship fired on Kronos One while it was under escort by the USS Enterprise, making it appear as if the latter ship had fired upon the Klingons, violating the terms of the truce. This attack facilitated the boarding of Kronos One by co-conspirators from the Enterprise, who assassinated Gorkon. When Captain Kirk and Doctor McCoy boarded Kronos One to provide assistance and prevent a full-scale conflict from developing, Chang ordered them arrested and charged with Gorkon's assassination under the rules of Interstellar Law. He also served as the prosecutor for the state at Kirk and McCoy's trial, where he was successful in obtaining a conviction by forcing Kirk to admit that, as captain, he was responsible for the conduct of the crew under his command.
However, Chang was surprised that, due to the impending peace talks, the judge did not order the customary death sentence, but instead sent the pair to Rura Penthe. In an attempt to ensure Kirk and McCoy's death, Chang had the commandant arrange for the Starfleet officers to be killed while attempting to escape, therefore eliminating any suspicion as to the motive for the killings. Kirk and McCoy were ultimately rescued, however, by the Enterprise crew.
With time running out before the Khitomer Conference, Chang ordered his Bird-of-Prey to intercept and attack the Enterprise in orbit of Khitomer. His ship initially had the advantage in being able to fire while cloaked, causing considerable damage to the Enterprise and also scoring a hit on USS Excelsior, under the command of Hikaru Sulu, which had arrived to divert fire away from the crippled Enterprise. However, this advantage was eventually negated when Enterprise crewmember Captain Spock developed a means whereby a photon torpedo could be modified to home in on the plasma exhaust of Chang's ship. Chang and the other bridge officers were killed by the initial explosion of the modified torpedo, which allowed Enterprise and Excelsior to launch more torpedoes that destroyed the Bird-of-Prey. Reflecting his love of Shakespeare, his last words were "to be, or not to be", from Act 3:I of Hamlet. (Star Trek VI: The Undiscovered Country)
Chang was played by Christopher Plummer. Plummer reportedly requested that his character have more subtle Klingon makeup, giving Chang a more Human look than most Klingons in the Star Trek films. Chang's appearance, as well as his affection for the works of the Human playwright Shakespeare, may be explained in part by the Klingon augment virus that spread through the Empire in the mid-22nd century. Among its other effects, the virus dissolved Klingon cranial ridges and gave its victims a more Human appearance (see "Affliction"). One of Chang's ancestors may have been a "smooth-headed" Klingon who was exposed to the retrovirus. In the Star Trek Magazine Villain Special of 2009, Chang's part in the Khitomer conspiracy was compared to Colonel Claus von Stauffenberg, the architect of the failed plot to kill Adolf Hitler in 1944 (somewhat in reverse, as Chang's plot was successful and was intended to continue a war).
- The game Star Trek: Klingon Academy indicates that Chang lost his eye in a blood duel against the usurper Kalnor who attempted to gain control of the Klingon Empire.
- Also according to Klingon Academy, Chang had been a general at least since the 2260s, and commanded the fleet at the Battle of Organia before the Organians imposed their peace treaty.
- According to the novelization of Star Trek VI: The Undiscovered Country, Chang acquired the sobriquet "the Merciless" after commanding punitive attacks on enemies of the Klingon Empire (Dillard 1992, 69).
- Also according to the novelization, the name of Chang's prototype Bird-Of-Prey was Dakronh.
- According to A.C. Crispin's novel Sarek, taking place in the aftermath of Star Trek VI, the Khitomer conspiracy was found to have been started by a group of telepaths under Romulan control, and it was suggested that Chang, among other leaders of the conspiracy, were subtly influenced by them.
- Chang's mirror universe counterpart appears in the novel The Sorrows of Empire. Chang, as the senior military adviser to Regent Gorkon, advocated the construction of an entire fleet of Birds-of-Prey that could fire while cloaked, as the ultimate weapon to bring down the Terran Empire. These fleet played a vital role in the conquest of its successor state, the Terran Republic, by the Klingon-Cardassian Alliance in 2295.