It looks like Star Wars: The Rise of Skywalker is bringing the red Force lightning seen in Legends to the films. The Skywalker saga that has been built since the first Star Wars film in 1977 is coming to an end with Star Wars: The Rise of Skywalker, the third installment in the sequel trilogy. Directed by J.J Abrams, the film is bringing back Rey (Daisy Ridley), Kylo Ren (Adam Driver), Finn (John Boyega), Poe Dameron (Oscar Isaac), and Rose Tico (Kelly Marie Tran) along with old friends like Lando Calrissian (Billy Dee Williams) for one last adventure.
Plot details on Star Wars: The Rise of Skywalker are still a mystery, but it’s set a year after the events in Star Wars: The Last Jedi, and will follow the Resistance (or what’s left of it) as they face the First Order one more time, all this while the Jedi/Sith conflict reaches its peak. Because secrecy is key, the trailers haven’t revealed much (although they have been a good source for all types of theories) but the poster contains a hint at an element from Star Wars Legends that might be making its way to the film saga: red Force lightning.
The official poster for Star Wars: The Rise of Skywalker shows red Force lightning coming from Kylo Ren. While Force lightning has appeared in the film saga before, this would be the first time red Force lightning is used on the big screen. Force lightning is a power that can be conjured by Force users through the dark side - but that doesn’t mean it’s exclusive to the Sith, as some Jedi have used it multiple times. However, as it’s commonly used as an offensive technique and torture method, it’s typically associated with dark side Force users.
Force lightning can cause serious damage to people on the receiving end, either immediate or long-term. Its first appearance in the films was in Return of the Jedi, when Darth Sidious tortured Luke Skywalker with it. However, red Force lightning has only been seen in Star Wars Legends (which, of course, isn't canon), coming from Darth Desolous, Darth Tenebrous, Son, and Darth Maul. Considering that Lucasfilm has been changing and incorporating parts of Legends into Star Wars canon, this could just be the next element.
Kylo Ren hasn’t shown to have the mastery needed to use Force lightning, but his master, Supreme Leader Snoke, used it to subdue him, and with Palpatine/Darth Sidious returning in The Rise of Skywalker, it’s quite possible that Kylo will learn to conjure the amount of dark Force required to use Force lightning. With Rey having a strong connection to the Force and being a quick learner (with a clear temptation towards the dark side, too), it wouldn’t be surprising if she uses Force lightning as well to defend herself against Kylo Ren and his red Force lightning.
Adding the red Force lightning to the films wouldn’t make Star Wars Legends canon again, but it would at least acknowledge an important element from that alternate timeline. Now it’s just a matter of waiting for Star Wars: The Rise of Skywalker to see if Kylo Ren has always been able to use the red Force lightning, if he will learn from another powerful character, and how (and against who) he’ll use it.