FALL OF THE REPUBLIC
The Nightsisters, an ancient matriarchal order of Force-using witches, ruled Dathomir during the Clone Wars, spurning all alliances and regarding outsiders with suspicion.
The Nightsisters’ rule of the planet came undone when their leader, Mother Talzin, agreed to help Asajj Ventress avenge her betrayal at the hands of Count Dooku. The Nightsisters tried to assassinate Dooku, and then sent him a new apprentice, Savage Opress, who was secretly loyal to them.
The Nightsisters’ plots against Dooku failed and he sent General Grievous to wipe out the order. The Nightsisters fought back with ancient spells, but were overwhelmed and massacred, leaving their rule little more than a memory.
THE DARK TIMES
In order to fully unlock the secrets glimpsed in the Jedi and Sith holocrons, Maul, the former Sith, took Ezra Bridger to his home planet of Dathomir. There, Maul used Nightsister magic to obtain the knowledge they were seeking. While the dark ritual proved successful, the spirits of the Nightsisters were awakened, and they demanded payment in the form of host bodies. Eventually, Maul escaped, and Ezra struck the Nightsisters’ sacred altar, vanquishing the specters.