The Unforgettables started as a Rebel cell. Their first action was to wipe the memories of the entire droid complement of a new Star Destroyer.
History
Although they started as just a rebellious group of pranksters, when their leader was captured attempting another memory wipe and indefinitely imprisoned, they quickly accelerated their campaign against the Empire. They vowed to wipe any droid important to the Imperial presence. They started wiping servant and protocol droids. They then moved to wiping droids that performed important functions like starport-control and other duties vital to civilians. This lead them to be denounced by the Rebel Alliance and the Unforgettables were soon hunted by the Empire and Rebel Alliance alike.