Star Wars fans know that a Sith lightsaber is always red, and they know that the color comes from the Kyber crystals inside the weapons. In Charles Soule's Darth Vader #1, which is considered Star Wars canon, the explanation behind those crystals is finally given.
The new comic was released this week, and it tells the story of Darth Vader's training with the emperor. At one point, the curious student asks his master about the red sabers, and how they all get to be that color.
According to Palpatine, the crystals are red because the Sith cause the objects to bleed. Yes, the crystals actually bleed.
The emperor goes on to explain that the red crystals all used to be regular crystals from Jedi lightsabers. However, since the crystals are living beings, they can feel pain.
The Sith need to remove those crystals from the Jedi, use the dark side, and pour their pain into the crystal, causing it harm in the process.
This is the exact explanation the emperor gives:
"The crystal from any Jedi's saber will do. As you know, the Kybers are alive, in their way. Like any living thing, they can fell pain. Through the dark side, you must pour your pain into the crystal. And when, at last, the agony becomes more than it can stand...a beautiful crimson. The color of your rage."
Well, there you have it, the rage of the Sith turns a lightsaber red. Hopefully, as the comic goes on, everyone will get to see who Vader took his crystal from.
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Star Wars: The Last Jedi is the second film in the new Star Wars sequel trilogy that began with Star Wars: The Force Awakens in 2015. The film will deal with Luke training Rey to become a, and possibly the last, Jedi. Meanwhile, the Resistance, including Poe Dameron and First Order defector Finn, continues to fight against the First Order, led by General Hux, while Supreme Leader Snoke and his Dark Side follower Kylo Ren continue their mysterious plot.
Star Wars: The Last Jedi is written and directed by Rian Johnson and stars Mark Hamill, Carrie Fisher, Adam Driver, Daisy Ridley, John Boyega, Oscar Isaac, Lupita Nyong'o, Domhnall Gleeson, Anthony Daniels, Gwendoline Christie, Andy Serkis, Benicio Del Toro, Laura Dern, and Kelly Marie Tran.