General Chang was a Klingon military officer and chief of staff to Gorkon, Chancellor of the Klingon High Council in 2293. In that year, Chang was involved in the Khitomer 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.
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 on the suggestion of Commander Nyota Uhura. 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 requested that his character have more subtle Klingon makeup, giving Chang a more Human look than most Klingons in the Star Trek films. Plummer commented: "I found a lot of the headgear that some of them wore rather phoney. I could see where the stitches were, so I decided I'd be a little different". Plummer thought he looked like Israeli military leader Moshe Dayan. ("Klingons: Conjuring the Legend")
John Colicos commented when filming "The Sword of Kahless" as Kor: "I tried to get rid of my wig but they wouldn't go for it. I guess you have to be Christopher Plummer before they'll let you be a bald Klingon". (The Official Star Trek: Deep Space Nine Magazine issue 18, p. 24)
In the Star Trek Magazine issue 149, the "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).
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. Also, he lost an eye and wore a eyepatch similar to Claus von Stauffenberg.
From the Star Trek Encyclopedia (4th ed., vol. 1, p. 132), Chang's "demand in court that Kirk answer a question without waiting for a translation is a paraphrase of American ambassador Adlai Stevenson, who made the same demand of Soviet ambassador Valerian Zorin at the United Nations during the Cuban missile crisis in 1962."
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. It also stated that 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). The novelization also states the name of Chang's prototype Bird-Of-Prey was named the IKS 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 (β) 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. This fleet played a vital role in the conquest of its successor state, the Terran Republic, by the Klingon-Cardassian Alliance in 2295.
The alternate reality version of Chang appears in the comic crossover mini-series Star Trek - Green Lantern: The Spectrum War where he serves in the Klingon Defense Force and commands the Bird-Of-Prey, IKS Muqtovor. Following Captain James T. Kirk's excursion to Qo'noS in 2259, Chang spent months without cease hunting him down and bring him to justice. In 2262, Chang finally caught up with Kirk in the vicinity of the unexplored Nodell-16 system. Just before attacking the USS Enterprise, Chang was then chosen by a Yellow Lantern Power Ring that had crossed over from another universe to be its bearer. With his new power, Chang creates a Muqtovor to attack the Enterprise, but was blocked by Green Lantern Hal Jordan and they proceeded to fight. After the Enterprise retreats, Chang returned to Qo'nos and entered the Great Hall to meet with the High Council. There, he killed their guards and the council members and claimed the title of Emperor of the Klingon Empire for himself. He then meets Thaal Sinestro, leader of the Sinestro Corps who came from the same universe as the ring. Sinestro easily overpowers Chang, but he soon agrees to assist him in eliminating the enemies of the Empire. They later fight Atrocitus, leader of the Red Lantern Corps and the Gorn Glocon, who had been chosen by a Red Lantern Power Ring during their attack on Starbase 12, until the Enterprise arrives. He then fights against Larfleeze, leader of the Orange Lantern Corps and the Romulan Decius, who had been chosen by an Orange Lantern Power Ring until Sinestro surrendered. The battle between the Lanterns ends when the Power Rings choose Spock to bear the entire emotional spectrum in order to defeat Nekron, with the Life Entity on the newly resurrected Vulcan and without the protection of their rings, Chang, Glocon and Decius die in the vacuum of space.