Garoche Tarkin was a Human male who served in the Imperial Navy since the earliest days of the Galactic Empire. A scion of the wealthy and influential Tarkin family of the planet Eriadu, Garoche was the son of Grand Moff Wilhuff Tarkin. Shortly before his disappearance around 19 BBY, Garoche had reached the rank of admiral and was in command of a Imperial I-class Star Destroyer.
Following in the footsteps of his father, then-Moff Wilhuff Tarkin, Garoche Tarkin enlisted into a military academy, thus also keeping in tradition with his family's strong support for military service. While training at the Academy, he befriended his rival and fellow cadet Shale. By 19 BBY, he was serving the Galactic Empire as an admiral and commanding officer of a Imperial I-class Star Destroyer.
Barely after the fall of the Old Republic and the rise of the New Order, Admiral Tarkin was tasked with eliminating insurgents in the Ghost Nebula. However, the mission had apparently been a failure, resulting in the disappearance of both the admiral and his vessel. In order to find and retrieve his missing son, Grand Moff Tarkin requested the aid of Emperor Palpatine. Much to the dismay of Tarkin, however, the Emperor's Sith apprentice Darth Vader was tasked with the mission to find Garoche. In the event that Vader became distracted from his primary objective, as had happened in the past when faced with hunting down Jedi fugitives, Tarkin attached Captain Shale to the mission.
In actuality, Garoche defected to Atoa in part due to a deep resentment of the atrocities he had to commit in the name of Palpatine, and aided in its insurgency after the Lady Saro, High Priestess of Atoa, forgave him for his crimes. The pair became lovers. Captain Shale had followed him into defection, with the former seeking to kill Lord Vader, but failed and ended up dead. He later appeared with Saro after the latter removed the ghostly image of Padmé Amidala, Vader's wife. Garoche and Saro then persuaded for Vader to repent of his sins. Vader ultimately killed them both in an attempted suicide by collapsing the cathedral they were in to atone for his sins. Vader However ultimately survived, blaming Garoche's death on the Atoan Insurgents, part of a plan with the Emperor to deepen Wilhuff Tarkin's hatred and make him a better tool of the Empire.
True to Palpatine's plans, Garoche's death led to his father committing genocide against the Atoans as revenge for their perceived part in his demise.
Ultimately, however, Garoche and Shale would prove to not be the only Imperials disgusted with having to commit several atrocities in the Emperor's name. The Imperial Academy headmaster, Gentis, would orchestrate a military coup against Palpatine shortly afterwards in order to stop him and his warmongering ways.