Dathomir was a remote, neutral planet in the Dathomir System and the home of the Nightsisters, an order of witches strong in the dark side of The Force. Dathomir was also home to the Nightbrothers, Zabraks who were ruled by the Nightsisters.
In his youth, Maul was taken from Dathomir as a child by Darth Sidious, who trained him as his apprentice and employed him as such until Maul was defeated by Obi-Wan Kenobi on Naboo. Sidious had other dealings with Maul's mother, Talzin, who eventually rose to become the leader of the Nightsisters. Count Dooku, Sidious' apprentice after Maul, later came to Dathomir in search of a new assassin after the apparent demise of his previous apprentice Asajj Ventress, who had also been born on Dathomir. As part of a plot by the Nightsisters to help Ventress achieve revenge on the Sith, the Nightsisters presented Dooku with Maul's magically altered brother Savage Opress to serve as his new assassin and apprentice.
However, when the time came for Savage to help Ventress destroy Dooku, the ensuing conflict resulted in Savage cutting ties with both of them and returning to Dathomir in search of Talzin's help. From Talzin, Savage learned that Maul was still alive and set out to find him; while he was gone from Dathomir General Grievous led the Separatist Droid Army in an invasion of Dathomir in retaliation for the Nightsisters' attacks on Dooku, leading to the deaths of all the members of the clan but Talzin and Asajj. The two Zabrak brothers eventually returned, and Talzin restored Maul's sanity and gave him a new set of droid legs; both she and Savage would later perish at the hands of the Sith, while Asajj was later laid to rest on Dathomir after briefly allying with the Jedi. Maul would later return to Dathomir on at least one occasion, and in the former stronghold of the Nightsisters stored a collection of artifacts he had acquired, such as the Darksaber.