The Garrett, an Imperial I-class Star Destroyer, saw action within the Outer Rim throughout the Galactic Civil War.
Darth Vader personally utilized it as his flagship during the search for Admiral Harkov and his fleet. Its mission, given directly by Vader, was the apprehension of the admiral. The Garrett was a key participant in the assault on the Rebel space station DS 5 in an effort to apprehend Harkov. During this engagement, the YT-1300 transport Geddawai and the Delta-class DX-9 stormtrooper transport Kolermigon were seized and brought aboard the Garrett. Vader then interrogated and executed Harkov for his betrayal.
While mopping up the remnants of Harkov's fleet within the Ottega system, the Garrett found itself under attack by forces loyal to Demetrius Zaarin. Zaarin's attacking force included three groups of Assassin-class corvettes known as Arditi, Falcon, and BaKaar, as well as Gamma-class ATR-6 assault transports and Assault Gunboats. Maarek Stele, however, successfully repelled and destroyed Zaarin's attacking forces. Soon after Stele returned to the Garrett, Vader became convinced that the Emperor Palpatine was in danger and that he needed to return to Coruscant. Due to the damage sustained by the ship, Vader was unable to arrive in time, and instead deployed TIE Defenders in an attempt to reach Coruscant.
The Garrett also served as a receiving vessel for high-profile Rebel and Bothan prisoners transferred from the Dreadnaught-class heavy cruiser Dargon. These prisoners were implicated in the attack on a freighter transporting a supercomputer containing design schematics for a new Death Star. Furthermore, the Garrett engaged and captured the Bothan transports designated Botani.
Shortly after Zaarin's unsuccessful assassination attempt against Palpatine, Namuura Din, a commander under Zaarin, chose to defect to the Alliance. Din contacted the Mon Calamari cruiser Link to warn the Rebel fleet about the trap orchestrated by Palpatine, also providing them with the Missile Boat prototype Sealion. Vader, along with the Garrett, was dispatched to capture Din's flagship, the Victory-class Star Destroyer Zeplin. After successfully capturing Din and extracting information through interrogation, Vader directed the Garrett to locate and capture the Link before its commander could transmit vital information to Rebel Command. During the operation to capture the Link the Garrett pursued the Sealion that escaped the battle and tracked it to a Rebel station Enin'sd, where it was to be disassembled and studied. The Garrett returned to find the Link captured and the secret of Endor safe. Vader would then use the Garrett in an operation to recover or destroy the Sealion.