Separatist holdouts (Dark Times)

"There exist surviving remnants of the former Confederacy still out there. Reactivated droid armies and pro-Separatist militias continue to wreak havoc on the galaxy and for our new empire to survive we must defeat them immediately."

- Wilhuff Tarkin describing the Separatist holdouts

The Separatist holdouts also known as the Separatist remnants was an umbrella organization comprising of surviving political and military remnants of the Confederacy of Independent Systems and Separatist-aligned groups, militias, and fleets that survived the Clone Wars and avoided being absorbed by the Galactic Empire at the end of the war in 19 BBY. They were composed of reactivated remnants of the Separatist Droid Army, surviving fleets of the Confederate Navy and pro-Separatist militias that continued fighting long after the shutdown command.

Overview
Following the execution of Order 66, the newly inducted Sith Lord, Darth Vader, traveled to Mustafar where he proceded to execute the members of the Separatist Council and their security details as well. Afterwards Vader activated the shutdown command which shutdown most of the droid army which paved the way for the empire to occupy most of the remaining Separatist worlds, though some worlds reactivated their own droid forces and/or restarted droid factories and produced new droids to fend off the inevitable Imperial invasion of their systems. Other Separatist worlds simply formed militias during the war and they kept fighting even after the shutdown command was given and resisted the Empire once they began to invade their native systems.