The Great Mothers were three Dathomirian Nightsisters who allied themselves with Imperial Grand Admiral Mitth'raw'nuruodo. Their names were Klothow, Aktropaw, and Lakesis, and they were practitioners of dark magick, claiming to be able to read the threads of fate and destiny.
Operating from a fortress on the extragalactic planet Peridea, the Great Mothers were three Nightsister witches who were descended from the fallen Witch Kingdom of the Dathmiri. The Witches were aware of the Jedi Order and hostile to it. Eventually, the Witches were found and awakened by the exiled Grand Admiral Mitth'raw'nuruodo "Thrawn," who allied with the Witches in the hope of escaping exile back to his galaxy. They helped Thrawn's forces survive on Peridea. In return for reaching out to Thrawn's former accomplice Morgan Elsbeth, the Witches, along with a gathering of cargo from their catacombs, were promised passage to the galaxy along with Thrawn's forces.
Baylan Skoll and his apprentice, Shin Hati, also suspected that the three wanted to leave Peridea to flee a power greater than their own. Following their escape from Peridea, the Witches and the rest of the Chimaeras personnel made their way to the planet Dathomir with the collected cargo.
The Great Mothers first appeared in "Part Six: Far, Far Away," the sixth episode of the Ahsoka television series. In Greek mythology, the Fates were three goddesses who read and determined destiny by spinning, measuring, and cutting the threads of fate. Their names were Clotho, Atropos, and Lachesis, names similar to those of the Great Mothers.