Shadow Collective

Less of a distinct organization of itself and more of a conglomerate, the Shadow Collective rose to prominence thanks to the work of the returned Darth Maul and his brother-turned-apprentice, Savage Opress, as the former Sith attempted to enact revenge on the Jedi that had attempted to kill him, decades prior, Obi-Wan Kenobi, and the master that had abandoned him, Darth Sidious. Maul and Opress gathered power from a hodgepodge of forces, including fellow crime families: at its brief height, the collective included the Mandalorian Death Watch, Black Sun, Crimson Dawn, the Pyke family, the Nightbrothers and sisters of Dathomir, and even elements of forces from the Hutt cartels, making them the de-facto ruling power of the underworld by the final months of the Clone War.
It wasn’t to last, however: after Maul made his play for power public by working with Death Watch to attempt a coup against the ruling powers of the planet Mandalore, the rogue Sith was confronted squeezed by both Republic intervention on the neutral world and an encounter with his former master. Maul’s brief captivity at the hands of the Republic (about to become the Galactic Empire) and the death of Opress at Sidious’ hands created a power vacuum that lead to the Shadow Collective’s members going their separate ways once the remnants of the Separatist forces turned on them, bringing an end to its influence on the galaxy.