Ren will be revealed as the new canon version of Brakiss
Ren seems to be young enough to have been active during the Galactic Civil War. In the Star Wars Legends continuity, Brakiss served the Galactic Empire as part of the Inquisitorius. Perhaps Ren was one of those children recruited to hunt down the surviving Jedi. The only problem here is that the Inquisitorius are implied to have been Killed Offscreen before A New Hope, but who says that any of them didn't survive the ordeal in case they were all dispatched?- Jossed. He's never referred to as Brakiss and bears no resemblance to the character besides superficial traits (evil Force-user, similar physical features). It's never mentioned he was an Inquisitor, though Ren's backstory is never explored in-depth at all, so who knows.
The Knights of Ren are Combat Sadomasochists
Ren nearly grabs ahold of his own lightsaber blade with his bare hand (I don't think he makes open contact, but logically it still can't have felt good). His torso is covered in burns of, thus far, unknown origin. In The Force Awakens, Kylo Ren pounds on an open, bleeding wound in his side to focus his anger. All this points to self-harm being part of their combat doctrine. Ren will be killed by Kylo Ren to take over his leadership
In The Force Awakens and The Rise of Skywalker, Ren is nowhere to be seen among the Knights of Ren. How this can be possible if he was their leader? Easy, Kylo Ren killed him to take over the Knights of Ren for himself. Either this or Kylo deposes Ren from his title and sends him into exile.- Confirmed. In the final issue, Kylo kills Ren and is accepted as the Knights' new leader.
Luke Skywalker found out about Darth Plagueis the Wise
Hence how Luke got the idea of killing Ben during his sleep.- The novelization of The Rise of Skywalker confirms that Luke learned about Darth Plagueis from his father, but not in the context of Luke's instinctive reaction to Ben's darkness. Darth Plagueis is not mentioned in The Rise of Kylo Ren.
Albrekh will make an appearance in the last issue to forge Kylo Ren's mask
In The Rise of Skywalker, the Sith alchemist Albrekh repairs Kylo Ren's mask after its destruction in The Last Jedi. As the Visual Dictionary of Episode IX states that Albrekh serves the Knights of Ren is a metalsmith, perhaps he designs their weaponry and equipment? If he designs Kylo's mask, then it has much sense that Kylo asked him to repair it.- Jossed. We don't see how Kylo got his mask in the comic.
This mini-series will be followed by a Kylo Ren ongoing written by Charles Soule.
