As Starkiller makes to strike Darth Vader down, he is stabbed from behind by a hooded figure, who fades in out of nowhere, as if he had been watching the entire battle. General Rahm Kota attacks him, yet is easily slashed across the stomach. He and his soldiers are blasted of the platform and into the sea. Meanwhile, Terror Troopers make short work of PROXY and other Rebels. Vader tells the dying Starkiller that he lied about the cloning process not being perfected; the hooded figure revealing himself to be the only 'perfect' clone of Starkiller, pale and deeply immersed in the Dark Side. Starkiller succumbs to his wound, and dies. Darth Vader congratulates the reborn Starkiller for completing his training. He orders him to take the Rogue Shadow and search the stars for the surviving Rebels, and to kill them all. As the clone turns to leave, he briefly glances at the dead body of Juno Eclipse with no apparent emotions, except hate. The clone takes the Rogue Shadow, accompanied by several TIE Fighters, and makes the jump to hyperspace.
In response to the threat posed by the Rebel Alliance during the Battle of Endor, the Dark Apprentice is ordered by Darth Vader to prevent the Rebels from destroying the Endor shield generator bunker so as to prevent any risk of the new Death Star's destruction. In order to preserve the secrecy of his existence, the Sith Lord instructs the clone to leave no survivors in the wake of his destruction, thus including Imperial troopers as targets as well. After landing the Rogue Shadow on Endor, the reborn Starkiller navigates his way through the forest-wide moon, killing dozens of Rebels and Ewoks alike. By the time he reaches the Imperial bunker, Han Solo and Chewbacca remained in front of the entrance to stall the Dark Apprentice while Leia and her commandos attempted to destroy the bunker from within.
Using a commandeered AT-ST Walker, Chewbacca tries to kill the clone with the aid of Solo and a group of Ewoks. Their efforts prove to be futile, however, as the Dark Apprentice kills the indigenous creatures and disables the Walker. After climbing aboard the Walker, the clone engages Chewbacca and easily overpowers the Wookiee. While the Dark Apprentice held Chewbacca by the throat, Solo tried to save his friend by shooting the clone but instead accidentally kills Chewbacca, whom the clone used as a body shield. Solo fired several more shots at the clone, only to watch as they were all effortlessly deflected by the clone's lightsaber. The Dark Apprentice then gripped Solo through the Force and pulled him towards his lightsaber, thus impaling the former smuggler. With both Chewbacca and Solo dead, the apprentice entered the base to complete his mission.
Inside the bunker, the Dark Apprentice arrived in time to see Rebel soldiers engaged in battle with Imperial troopers, who were committed to protecting the shield generator. Obeying Vader's orders to the letter, the clone killed all that stood in his path. He eventually encountered Leia, who retreated further into the bunker while her commandos attempted to buy her the time she needed to destroy the generator. But the Rebels failed and the clone pursued the Rebel princess until he finally encountered her at the core of the base. To his surprise, Leia removed her Rebel gear to reveal her Jedi attire and brandished a yellow-bladed lightsaber. According to Leia, the death of her twin brother, Luke Skywalker, at the Battle of Hoth necessitated her training as a Jedi Knight.
Leia demonstrated remarkable skills in lightsaber combat and Force techniques while dueling her father's apprentice. Using the Force to enhance her strength, speed and agility, Leia was able to hold her own against the clone for a short while. But even Leia's training was not enough to enable her to overcome the raw power and superior skills of the Dark Apprentice. Leia, outmatched both physically and in the Force by the clone, tried to use the bunker's defenses to kill her opponent, only for that to backfire as well. When the duel moved outside to the top of the bunker, Leia tried once more to defeat the Dark Apprentice with her lightsaber and Force powers, only to be pushed on the defensive as the clone countered her offensive with a relentless assault of his own. Ultimately, the apprentice merely toyed with Leia by sparing her in a few instances when he could have easily killed her. The end of the duel, and the Rebel Alliance's last hope for victory, came when the Dark Apprentice impaled Leia with his lightsaber, thus killing the last offspring of Anakin Skywalker.
On the Death Star, Emperor Palpatine and Darth Vader sensed the defeat of the Rebels on Endor. With the bunker secured and the shield generator still active, any chance that the Rebel fleet had of destroying the battle station with the two Sith Lords on it was gone. Just after Palpatine declared that the end of the Alliance marked a new golden age of peace for the Galactic Empire, he revealed his awareness of his apprentice's latest act of treachery. True to his nature, Palpatine gloated about how he knew about Vader's attempts to clone the original Starkiller since the beginning of the secret project on Kamino. In a desperate attempt to rid himself of his Master, Vader activated his lightsaber in order to strike down the Emperor. But Palpatine anticipated his apprentice's intention and countered with Force lightning, calling him Skywalker before doing so. Unable to bear the pain and the damage that the lightning caused to his armor's life support systems, Vader quickly fell to his knees in submission. The Emperor then commanded Captain Sarkli to take his forces to Endor and kill the clone.
As a group of Imperial Star Destroyers converged on the Dark Apprentice's location, the clone sat in meditation while Leia's corpse lay near him. As the vessels approached him, the apprentice opened his eyes with no trace of fear in them as he prepared to deal with the latest threat to himself and his Master's plans.