The Nightsisters were the ruling clan of of the Witches of Dathomir, who embraced the usage of dark arts within their Force-driven Magics. The Nightsisters were originally members of other witch clans who began to utilize the dark side in defiance of the light-sided orthodoxy found in the Book of Law—the governing holy text of the Dathomiri. These witches adopted a shamanistic culture that rejected the notion of "good" and "evil", and instead chose to call upon the twin energies of the Winged Goddess and the Fanged God in order to utilize their Magicks and communicate with the spirit realm. They focused extensively on the art of casting Force illusions through "illusion spells." Witches found guilty of practicing these heretical techniques were banished into Dathomir's wilderness and left for dead. However, in the final decades of the Galactic Republic's reign, the exiled witch Gethzerion used her superior powers to unite the wandering outcasts into a new clan—the Nightsisters.
Operating under a revised holy text known as the Book of Shadows, these sorceresses used their powerful connection to Dathomir's untamed wilds to terrorize their fellow clans and fight for dominance over the planet. Although the witches had designs for galacticdominance, they were largely confined to their own world, as the Jedi Order maintained active interdiction of the planet. The Nightsisters themselves were divided into various competing clans of their own until approximately 32 BBY, when Clan mother Zalem attempted to use Dathomir's legendary Infinity Gate to destroy Coruscant, the capital world of the Galactic Republic. After the plot was foiled and Zalem was killed by her daughter, the numerous clans of Nightsisters were united into a single coven by the shaman Mother Talzin. During the Clone Wars, the Nightsisters came to the forefront of galactic notoriety when Talzin transformed her people into a mercenary society that trained in combat and Magick so that their services as bodyguards, assassins, and soldiers could be sold to off-world bidders.
The time of relative prosperity would come to an end when the clan was drawn in the Clone Wars when Talzin tried to eliminate CountDooku with former Sister Asajj Ventress, but their assassination attempt failed. Sending General Grievous and a Confederacy of Independent Systems army to Dathomir, Dooku assaulted the Nightsisters' Fortress. The ensuing battle resulted in the near-extermination of the Nightsisters, though enough survivors remained for the Nightsisters to eventually resume their dominant position in Dathomir's affairs.
During the Imperial Period, the Galactic Empire maintained a significant presence on Dathomir, but after the Dark Lord of the Sithand Galactic Emperor Palpatine came to understand the depths of the Nightsisters' power and the strength of their founder, Gethzerion, he resumed the Jedi's former quarantine of the planet in an attempt to ensure that none of the witches escaped off-world. Despite Palpatine's efforts, many of the Nightsisters were able to flee Dathomir by allying with the criminal Zann Consortium. In the final years of the Emperor's reign, Dathomir was placed under the command of Zsinj, an Imperial admiral who declared himself a warlord after Palpatine's death in 4 ABY. Zsinj maintained the Emperor's forced isolation of Dathomir until 8 ABY, when Gethzerion and her Nightsisters succeeded in capturing New Republic General Han Solo on the planet's surface. The Clan Mother brokered a deal with the Imperial Warlord to trade General Solo for interstellar transport, but reneged on the arrangement and attempted to flee Dathomir without Zsinj's blessing. In retaliation, Zsinj directed his forces to destroy Gethzerion's transport, thereby killing her and all the Nightsisters aboard. This betrayal fragmented the Nightsisters, however the witches were able to reorganize by around 23 ABY, when Tamith Kai and her new Nightsisters allied with the Second Imperium faction of the Imperial Remnant. The clan survived through the Second Galactic Civil War and in 43.5 ABY, briefly allied with a Lost Tribe of the Sith Order against the New Jedi Order.