In Star Wars episode 9 we will see Kylo's lightsaber...however let's go over a theory I have regarding the use of Luke's GREEN lightsaber crystal. I believe Kylo took his lightsaber upon the destruction of the Jedi Temple (we saw flashbacks in The Last Jedi) and tried to make it bleed, however, he failed. If he didn't take Luke's, then he made his own crystal bleed, and failed. This is my theory on why his lightsaber flickers and what we could possibly expect...who knows until Episode 9 comes out. What do you think? That'd be cool if he's using Qu-Gon Jinn's lightsaber that Luke Skywalker took from Obi-Wan Kenobi's possession.