During the Imperial Era, specifically in 3 BBY, Starkiller received a mission: travel to the planet Felucia and eliminate Master Shaak Ti. She was one of the few remaining Jedi Council members. He was trained in the dark side of the Force as the secret apprentice and dedicated assassin of the Sith Lord Darth Vader. Starkiller's upbringing centered on the ruthless elimination of his master's adversaries, especially the Jedi who evaded Order 66 and the rise of the Galactic Empire. Vader assured Starkiller that facing Shaak Ti would be the ultimate test, so the apprentice journeyed to Felucia, driven to demonstrate his value and become a true Sith Lord.
Shortly after his arrival on Felucia, Starkiller encountered resistance from the Felucian inhabitants. Shaak Ti had enhanced their natural prowess with the Force. Starkiller battled through Felucia's jungles and eventually confronted Ti at the Ancient Abyss, a mega-Sarlacc held sacred by the Felucians. The ensuing lightsaber duel saw Ti fighting alongside Felucian warriors and the mega-Sarlacc, but Starkiller ultimately overwhelmed her. Wounded and defenseless, Ti accepted her fate, willingly falling into the mega-Sarlacc after warning Starkiller about the Sith's history of betrayal.
Not long after Starkiller finished his second mission within the ruins of the Jedi Temple, he was given his most critical task yet by the Sith Lord Darth Vader. Vader used the holodroid PROXY to communicate with his secret apprentice, instructing Starkiller to proceed to the planet Felucia and assassinate Shaak Ti. She was one of the last surviving members of the Jedi Council who had survived Order 66 and gone into hiding. Despite Starkiller's successful missions against other Jedi Masters, like Rahm Kota and Kazdan Paratus, Vader considered victories over an "old man" and an "outcast" insufficient to truly validate his apprentice's potential. Eager to become a true Sith, Starkiller followed his master's commands without hesitation.
During the voyage to Felucia, Starkiller was too engrossed in his mission and the prospect of success to pay attention to Captain Juno Eclipse, the pilot of the Rogue Shadow. He avoided Eclipse's attempts at conversation, only issuing necessary orders. Upon arriving at Felucia, the vibrant and lively environment caused an emotional reaction in Eclipse. Starkiller inquired about her emotional state, sensing conflicting feelings within her. She reluctantly revealed her involvement in the Bombing of Callos and how her actions led to the Galactic Empire turning the planet into a desolate wasteland. Starkiller, indifferent to her moral conflict, stated that she had made the correct decision by strictly following orders.
After Eclipse landed the Rogue Shadow on Felucia, Starkiller departed to hunt for Shaak Ti. Unbeknownst to Starkiller, Ti had observed the Rogue Shadow's arrival and correctly deduced that Darth Vader had discovered her location and sent an assassin to kill her. After Maris Brood, a young Jedi padawan who had survived Order 66 and become Ti's apprentice, reluctantly agreed to stay out of the fight, Ti ordered her Felucian warriors to intercept Vader's apprentice.
As the Rogue Shadow left to await further orders in a secure location, Starkiller was ambushed by Felucian warriors. During the initial skirmish, Starkiller sensed the natives' natural affinity for the Force, concluding that Shaak Ti had trained them to control their abilities. To conserve energy for his main target, he swiftly eliminated the Felucians in his path. As he neared Ti's location, Starkiller developed a degree of respect for her skill and her ability to survive the galactic-wide persecution of the Jedi. However, he also believed that Ti's presence on Felucia disrupted the Force's natural balance. Therefore, Starkiller justified Ti's death as necessary to restore equilibrium between the Light and Darkness.
Despite their determination to protect Shaak Ti, the Felucians fell one by one in their attempts to stop Starkiller. Spotting a Felucian village from afar, Starkiller used the Force to tame a river-dwelling creature, allowing him to reach the village by water. Upon arrival, he discovered that the village was built atop a mega-Sarlacc, known to the Felucians as the "Ancient Abyss." To Starkiller's satisfaction, Shaak Ti awaited him near the village center, which was also the Sarlacc's maw. As the remaining Felucians avoided him, Starkiller confidently approached the Togruta Jedi Master.
Shaak Ti sat in deep meditation on one of the Sarlacc's concentric gums, untouched by the massive feeding tentacles or flexing teeth. Starkiller used telekinesis to rip a mushroom from the Sarlacc's skin and hurl it at Ti, who casually deflected it. Rising from her meditation, she accused Vader of cowardice for sending an assassin, prompting Starkiller to activate his lightsaber and prepare for combat. Ti initiated the duel with a spinning downward strike, throwing Starkiller off balance. He back-flipped, blocking her lightsaber with his own. His hood snagged on a Sarlacc tooth, and after tearing it off, Starkiller could only fend off Ti's attacks until he regained his footing. He leaped over her, falling down two layers of gums toward the Sarlacc's maw before jumping back up. Shaak Ti intercepted him, her rapid assault forcing him to send a bolt of lightning into the Sarlacc's flesh. The resulting tremors caused Ti to lose her balance, and she jumped back from his attack. Starkiller pursued, seizing the offensive.
Their battle moved to the lower rings of the Sarlacc. Starkiller improvised, slicing off teeth and throwing them at Shaak Ti, or slashing and shocking the flesh to keep the beast agitated. Ti countered by controlling the Sarlacc's distributed intelligence, sending its feeding tentacles after him. Near the pit's center, digestive byproducts made breathing difficult. Throughout the fight, Ti lectured Starkiller on Jedi philosophy, irritating the Sith apprentice.
As the battle neared its end, Starkiller drove Ti back into the Sarlacc's maw, assuming his mission was complete. However, Ti reappeared, perched on a massive tentacle. Using her Force-enabled control, she commanded the Sarlacc to attack Starkiller with its tentacles. After dodging the first two strikes, Starkiller climbed onto a tentacle as it recoiled. Unable to hold on, he nearly fell into the maw, becoming pinned between four tentacles. He blasted them apart with a Force repulse and launched himself back to the ground. When Ti charged off the Sarlacc, he deflected her strike, driving her back into the tentacles and unleashing a wave of Force lightning, engulfing her in the attack.
Shaak Ti regained her footing, but she was already dying. As she died, Ti told Starkiller that he was enslaved to Darth Vader's will, expressing disappointment because she believed he could be more than just Vader's slave. Her words disgusted the apprentice, who saw them as deceptive tactics to separate him from his master. In Starkiller's view, the remnants of the fallen Jedi Order had become weak and pathetic, a far cry from their former power.
Starkiller declared his loyalty to his master, vowing never to betray the Sith for the Jedi. Shaak Ti pitied the apprentice, warning him that the Sith always betray each other. She then fell into the Sarlacc pit, dying in a flash of Force energy. Starkiller left, satisfied that removing Shaak Ti's influence would allow the dark side to take hold on Felucia and restore balance. Returning to the Rogue Shadow, he reported his success to Vader, who declared that the time was right to assassinate Darth Sidious, known as the Emperor Palpatine. Starkiller barely concealed his excitement at the prospect of achieving the goal he had been raised and trained for since childhood. As he journeyed back to the Executor, Starkiller imagined his future as a true Sith Lord, ruling the Galactic Empire alongside his master.
However, upon his return, Starkiller found the Executor surrounded by the Emperor's fleet, consisting of Imperial Star Destroyers. Undaunted, Starkiller approached Vader and asked when they would strike down the reigning Dark Lord of the Sith. Vader explained that he had not summoned the fleet and then unexpectedly impaled Starkiller with his lightsaber, explaining that the Emperor's spies had tracked Starkiller and prematurely exposed their plot. Sidious, communicating through PROXY, angrily scolded Vader for high treason and violating the Rule of Two. Threatened with death, Vader seemingly "killed" his apprentice to comply with the Emperor's demands.
Six months later, Starkiller awoke on the Empirical, surprised to be alive. With PROXY assuming his form, Darth Vader explained to his outraged and restrained disciple that he had faked Starkiller's execution to deceive Darth Sidious. While Starkiller was unconscious, Vader repaired his damaged body. Promising vengeance on Sidious, Starkiller reaffirmed his loyalty to Vader, the Sith, and the dark side, ready for another mission. Vader tasked Starkiller with secretly creating an "alliance of rebels and dissidents" to distract the Emperor until the time was right to assassinate him.
On Felucia, Shaak Ti's death had severe consequences. As a beacon of the light side, she had kept the dark side at bay. Without her, the native Force-sensitive Felucians reverted to primal instincts and were consumed by the dark side. Maris Brood also succumbed to the dark side and the desire for power, having lost another Jedi mentor to the Sith. Soon after Starkiller left, the Empire's armed forces were sent to occupy and subjugate Felucia, a task that proved immensely difficult for the Imperial garrison.