Since the release of the novelization of The Last Jedi, everyone’s been looking for new content that wasn’t shown in the movie. In the novel, the scene with Luke’s going to kill Ben Solo is talked about with more description.
According to the novel, Luke sees a dark vision in Ben’s mind. He sees a burning temple, the dead, and heard people screaming along with lightsaber sounds. He sees what Ben will bring but he hesitates to kill Ben. Ben wakes up and…we all know how it ends. BUT. He claims to have heard several lightsabers not just one. This could only mean there were things already in motion, that there was already a group formed to rebel against Luke and the new Jedi order.
This could also be the Knights of Ren whom we still haven’t seen. Luke also says that Ben had these “veins of darkness” within him sort of like grandpa Ani. What would be nice to know is how Snoke got him to turn and who the heck the Knights of Ren are. We can only hope J.J. will do a good job tying loose ends and make things satisfying. I’m sure we’ll get a book on the Knights Of Ren soon to finally explain who they are. Hopefully.