Lagos served the Galactic Empire as a Sentinel-class landing craft. Following the obliteration of the Imperial Communications Center situated on Lothal, Lagos began transporting R4 courier droids back and forth to the Tellstar to preserve the Empire's lines of communication.
Following the Spectres, a rebel group, seizing authority over the Imperial Communications Center of Lothal, Grand Moff Wilhuff Tarkin gave the order to demolish the communications hub. Lacking the main communications center, the Empire resorted to using R4 courier droids for information transfer between locations, and the shuttle Lagos received the task of transporting these droids to the communications ship Tellstar, which was stationed in orbit around the planet.
When the rebels absconded with courier droid 264, they dispatched their mechanic member C1-10P, known as "Chopper," to take its place on Lagos. Their objective was to gather intelligence about Kanan Jarrus, their commander, who had been taken as a prisoner during the assault on the communications tower. Oblivious to the real courier's abduction, the personnel of Lagos transported Chopper to the Tellstar, enabling the rebel droid to duplicate communication records from the vessel.