Garoche Tarkin was a Human male who served the Imperial Navy from the very beginning of the Galactic Empire. Born into the wealthy and powerful Tarkin family on the planet of Eriadu, Garoche was the offspring of Grand Moff Wilhuff Tarkin. Prior to his disappearance around 19 BBY, Garoche had achieved the rank of admiral and commanded an Imperial I-class Star Destroyer.
Following in the path of his father, then-Moff Wilhuff Tarkin, Garoche Tarkin enrolled in a military academy, continuing his family's tradition of strong support for military service. During his training at the Academy, he became friends with his rival and fellow cadet, Shale. By 19 BBY, he was serving the Galactic Empire as an admiral and the commanding officer of an Imperial I-class Star Destroyer.
Soon after the fall of the Old Republic and the rise of the New Order, Admiral Tarkin received orders to eliminate insurgents located in the Ghost Nebula. However, the mission apparently failed, resulting in the disappearance of both the admiral and his ship. To locate and rescue his missing son, Grand Moff Tarkin requested assistance from Emperor Palpatine. Much to Tarkin's disappointment, the Emperor assigned his Sith apprentice, Darth Vader, to the mission to find Garoche. Concerned that Vader might be distracted from his main objective, as he had been in the past when hunting down Jedi fugitives, Tarkin assigned Captain Shale to accompany the mission.
The truth was that Garoche defected to Atoa, partly due to a deep aversion to the atrocities he was forced to commit in Palpatine's name. He aided their insurgency after the Lady Saro, High Priestess of Atoa, forgave him for his crimes. They became lovers. Captain Shale also defected, seeking to kill Lord Vader, but failed and died. Garoche later appeared with Saro after she removed the ghostly image of Padmé Amidala, Vader's wife. Garoche and Saro then pleaded with Vader to repent for his actions. Vader ultimately killed them both in an attempted suicide by collapsing the cathedral they were in to atone for his sins. Vader, however, survived, blaming Garoche's death on the Atoan Insurgents, as part of a plan with the Emperor to deepen Wilhuff Tarkin's hatred and make him a more effective tool for the Empire.
As Palpatine planned, Garoche's death fueled his father's genocide against the Atoans as revenge for their supposed role in his demise.
Ultimately, Garoche and Shale were not the only Imperials who felt disgusted by having to commit numerous atrocities in the Emperor's name. The Imperial Academy headmaster, Gentis, orchestrated a military coup against Palpatine shortly afterward in an attempt to stop him and his warmongering.