The clone of Kahless the Unforgettable, also known as Kahless II, was created by the clerics of Boreth in 2369 using DNA from the Knife of Kirom, a blade that was said to be stained with the blood of Kahless. The clerics and their scientists found a way to imprint specific information into the clone's mind. Specifically, they programmed him with the contents of the Klingon sacred text, stories and teachings of the original Kahless. Apparently, he was additionally programmed with a full knowledge of Klingon language and customs as well as how to defend himself in combat, although his lack of experience in combat proved to be problematic.
The clerics wished to give the impression it was the real Kahless who had returned from Sto-vo-kor to once again lead his people. When Worf visited the planet Boreth, the clone of Kahless appeared to him. With the USS Enterprise-D having been sent to bring Kahless back to the homeworld, Kahless accompanied Worf back to the ship, confident from Worf's tales of his comrades that they were honorable companions, approving of Worf's recognition of his Klingon heritage. Gowron attempted to test Kahless with the Knife of Kirom, but Doctor Crusher's subsequent analysis of the DNA confirmed that the blood on the blade and the blood of Kahless were identical.
Kahless and Worf spoke of a new direction for the Klingon people, but Worf began to doubt that the clone was the real Kahless, because he could not remember the taste of warnog, or what existence was like in Sto-vo-kor, although he claimed that this was because he was only a traveler who was allowed to pass between the worlds and thus had no memory of the other side while in this one. Kahless was challenged to combat by Gowron and was defeated, raising more doubts. In light of this, the clerics finally admitted their fraud. Although Worf's faith was briefly shattered by this news, a conversation with Data inspired Worf to consider what Kahless could be for the Empire as a symbol rather than define him by his origins. Worf thereby suggested that the clone of Kahless be made Emperor of the Klingon Empire; Gowron would continue to run the Klingon High Council and be the head of government, but Kahless could serve as a valuable reminder of what had once made the Empire great and encourage his people to remember their ways of honor. The clone of Kahless accepted and became the moral leader and the ceremonial head-of-state of the Klingon people. Before his departure from the ship, he told Worf that what mattered was Kahless's words and teachings, not the man himself, and as long as the Klingon people remembered those words it did not truly matter whether or not Kahless himself returned. (TNG: "Rightful Heir")
Emperor Kahless II refused to talk with Worf when he investigated the reason that a large Klingon fleet was docked at Deep Space 9 in 2372. Kahless' lack of power as emperor became evident several days later when the fleet launched an invasion of the Cardassian Union. Emperor Kahless condemned the invasion but was overruled by Gowron. (DS9: "The Way of the Warrior", "The Sword of Kahless")
Kor was unwilling to bring the Sword of Kahless to Emperor Kahless when he, Worf, and Jadzia Dax discovered it in the Gamma Quadrant in 2372. Worf had hoped Kahless would use the sword against Gowron. Kor, however, felt Kahless II was a "toothless figurehead" and a pretender to the throne. (DS9: "The Sword of Kahless")
|Leaders of the Klingon Empire|
|Emperors||Kahless I • Reclaw I • Reclaw II • Sompek • Mur'Eq • Kahless II|
|Chancellors||2151 Chancellor • 2153 Chancellor • M'Rek • Mow'ga • Gorkon • Azetbur • K'mpec • Gowron • Worf • Martok|
Emperor Kahless appears in The Left Hand of Destiny novels and the final Star Trek: A Time to... novels. In J.G. Hertzler and Jeffrey Lang's novels, Kahless helps Chancellor Martok to regain his position after a coup d'état against the Klingon leader. Kahless himself was believed to have been killed after fighting Hur'q soldiers on Boreth, although it is later revealed he survived. He stands down as Emperor, as he felt Martok's accomplishments had made him irrelevant, but would one day return if his people needed him again.
The book Kahless explores the myths behind the Unforgettable One. It goes into detail about how Morath was the honorable Klingon behind the revolt against Molor. It goes farther on to say that the blood on the knife that cloned Kahless was actually Morath's. That means that the clone of Kahless is really the clone of Morath.
In the PC game Star Trek Online, Kahless is still Emperor when the Fek'Ihri launch an invasion of the Empire from Gre'thor, and Chancellor J'mpok (Martok's successor) sends Klingon players to meet with him on Boreth. Emperor Kahless guides them into Gre'thor itself to do battle with the Fek'Ihri hordes, led by the vengeful spirit of Molor, and eventually against Fek'lhr in the heart of Gre'thor. After the Fek'Ihri horde is banished, Emperor Kahless gives the player a replica of the Sword of Kahless. Emperor Kahless resurfaces during the Iconian War storyline as the leader of "House Pegh", an order of Klingon infiltrators and assassins; during a raid on an Iconian facility, he is killed by the Iconian T'Ket in single combat, though the House Pegh operatives (aided by the player character and their away team) discover a critical weakness in the Iconians to exploit for the war to come.
In the miniseries Star Trek: Prey, a long-term plan set in motion by the descendants of Kurge results in the death of Emperor Kahless, prompting Worf to consider a suitable battle to earn Kahless the honor of entering Sto-vo-kor when he didn't die in battle.