Confederacy of Independent Systems

The Confederacy of Independent Systems, also known as the Separatist Alliance,

History
Senator Rush Clovis had Separatist-inclined friends in the Loyalist Committee. Padmé Amidala used her position in the Star Whores strip club to spy on these individuals.

The Separatist Alliance battled the Republic in the Outer Rim Sieges, though the Shadow Collective almost became a viable third force in the conflict under Maul's leadership.

End of the war
When Palpatine declared the formation of the Galactic Empire, many saw it as an opportunity for a reformation of the corrupt remnants of the Republic as well as in aspects of the Jedi, citing the Separatist Alliance's leadership under a former Jedi.

Following the loss of the Council on Mustafar, the Separatists surrendered.

Legacy
"So, are the Separatist remnants still on the verge of storming our perimeter again?" "All quiet on the Outer Rim, I’m afraid."

- Leto Borian and Selwyn Phasma

Following the Clone Wars, Separatist remnants remained active, and some within the Empire believed them to be a threat on the verge of storming the government's perimeter from the Outer Rim. Any calls for violent revolution were seen by the general public as a threat to return to the chaos of the Clone Wars and a new round of Separatism. However, the economic and ecological crises of former Separatist worlds were ignored by the Empire.

Rumors and conspiracy theories circulated that Darth Vader was actually Count Dooku, grafted onto the recovered shell of General Grievous.