The folks at Star Wars Galaxies have posted information about Exar Kun, a Sith Lord who will be the focus of an heroic encounter in Chapter 9.
Exar Kun began his Jedi training under Jedi Master Vodo-Siosk Baas. Clashes with his fellow students on Dantooine ended in a violent confrontation, showing hints of the dark side influencing Exar Kun's emotions even at this early stage in his training. Kun also studied the history of the Sith, Force-wielders devoted to the dark side.
Kun's impatience to learn more about the Force took him away from his studies on Dantooine. As he traveled the galaxy, he encountered the spirit of the Dark Jedi Freedon Nadd.
The spirit of Nadd exerted his influence and Exar Kun turned to the Sith and the dark side of the Force.
Read more here.