Nightsisters

Game Info
A tribe of Dark Side Force wielding witches found on Dathomir. They are known for keeping male slaves. Their leader (according to Star Wars Canon) is Gethzerion, found on the second floor of the Nightsister Stronghold. Another powerful Nightsister, Axkva Min, is also situated in the Stronghold under very heavy guard, and slaying her gains the player a Badge.

Star Wars Lore
The Nightsisters were a group of Dathomir Witches (usually exiled from their clan) who used the Dark Side of The Force. Before their defeat, their leader was Gethzerion, who endlessly terrorized the other Dathomiri Witch clans.

Due to Palpatine fearing the power of Gethzerion, he had all the ships stationed on Dathomir destroyed. The Nightsisters had then taken over the Imperial Prison, and enslaved all the stranded Imperials stationed there. Gethzerion had then made a deal with Warlord Zsinj that in exchange for turning over Han Solo, the Nightsisters would get access to a ship so they could escape the planet.

The Nightsisters were defeated after years of tyranny in 8 ABY, when the ship they were on was blown up by two of Zsinj's Star Destroyers.

Around 23 ABY, a new clan of Nightsisters was formed by Tamith Kai in the Great Canyon. This clan accepted males and treated them as equals instead of slaves. The best of the clan were sent to the Shadow Academy for more training, with the rest remaining in the Great Canyon. The fate of those left behind after the Shadow Academy fell is unknown.