Rule of Two
Years ago Darth Bane was a good person, but then his mind got dark because of the hidden desires he had in his mind. No one was able to believe that Bane will turn to the side of evil but he did. Not only he selected the side of evil, but he also became the master of that side and then he destroyed the rest of the Sith because he had a new rule in mind that he wanted to implement. He was of the view that there should be the rule of two in the Sith world.
This means that there should be one leader and one apprentice who would train under his guidance after which he will take the place of his leader. For this purpose, Zannah was the right choice as she had her intentions to embrace the dark side. Zannah was an apprentice which Bane was looking for and the moment he saw her, he was clear that she was the one he was looking for.
Bane started training Zannah but there were issues i.e the Jedi were coming for him and there wasn’t much time for the training. Drew Karpyshyn has also painted the character of Johun here who wants to take revenge on Bane because he killed the Jedi Master whom John was serving. The young Jedi wants to take revenge on Bane but it is not easy because Bane is going to the moon where he senses the strange power of the Force.
If he acquires that power then he would be unstoppable forever. Jonathan Davis i.e the narrator of the story also provides us the hint that Zannah has a few strange thoughts in her mind and she is not hundred percent psychologically. Path of Destruction and Star Wars: The Old Republic: Revan was going along the same pattern so the author decided to write something new for the fans. This one is about the rise of a new kind of evil in the world of Jedi and Sith.