This fleet was the navy of Gizor Dellso, a rogue Separatist who attempted to restart the Clone Wars.
The fleet consisted of Lucrehulk-class Droid Control Ships, Providence-class carrier/destroyers, Munificent-class star frigates, Vulture droids, Droid tri-fighters, Belbullab-24 strike bombers, and at least one Heavy Missile Platform.
After the Clone Wars were brought to an end by the Sith Lord Darth Vader in 19 BBY, Gizor Dellso, a Geonosian Separatist who was determined to continue the fight, traveled to planet Mustafar. There he managed to locate and reactivate a secret droid factory, which he used to produce an army of battle droids and a fleet of starships. Dellso sent the fleet to blockade Mustafar, to prevent any attacks of the Galactic Empire. Between 17 and 12 BBY, Vader became aware of Dellso's efforts to restart the Clone Wars, and sent the 501st Legion, the elite unit of the Empire, to eliminate Dellso and his droid army. Dellso's fleet engaged the Legion in space above Mustafar, where it was destroyed, and the factory was subsequently destroyed by the Empire.