Backlash - Aaron Allston

Three major storylines run through the Fate of the Jedi series. One is the odyssey of Jedi Grand-Master-in-Exile Luke Skywalker and his son Ben, as they travel from one world of non-Jedi Force-users to the next in search of clues as to what might have turned Jacen Solo to embrace the evil ways of the Sith Lords. The second is the attempts of Galactic Alliance Chief of State Natasi Daala to break the power of the Jedi Order, while young Jedi Knights on a variety of worlds are inexplicably going
insane. And the third is the tale of a previously unknown lost tribe of Sith as they rejoin the known galaxy determined to kill Luke Skywalker, destroy all the Jedi, and reinstate the Sith as supreme rulers. In Backlash, Luke and Ben will visit the deadly world of Dathomir, home to the Night Sisters, otherwise known as the Dathomiri Witches, as an ancient evil, released from its prison, stretches its hungry tendrils ever farther through the galaxy...