Kyber crystals are rare, Force-attuned crystals that grew naturally and are found on scattered planets across the galaxy including the planet Ilum, where Jedi padawans would come as part of their right of passage to build their lightsabers. They are used by the Jedi and Sith in the construction of their lightsabers. They can also be used by people who aren't Force-sensitive in weapons such as laser cannons aboard starships such as Kylo Ren's flagship, the Finalizer. Large kyber crystals can be used in superweapons such as the Sith Temple on Malachor and in the first and second Death Stars.
Kyber crystals were highly sought by Jedi, Sith, and people who weren't Force-sensitive due to their unique properties and their durability. The Death Stars were powered by an exceptionally large kyber crystal that was the source of their planet-destroying beams. Most Sith prefer to use synthetic kyber crystals (artificially created kyber crystals) to power their lightsabers. However, these crystals are highly unstable and could be explosive. Damaged kyber crystals, like the one powering Kylo Ren's lightsaber, are also unstable, and needed exhaust ports and focusing crystal activators to draw the excess energy away from the crystal to prevent it from exploding, resulting in his signature crossguard lightsaber. This also resulted in the ragged, flaming appearance and deep growling hum of his lightsaber's blades. A damaged kyber crystal can be repaired using healing techniques, as Rey did to the crystal of the Skywalker lightsaber after it broke during her confrontation with Kylo Ren on the Supremacy.
Kyber crystals are inherently attuned to the light side of the Force, and Sith could only use them by dominating them with the dark side of the Force and their will, which turns the crystals red, causing them to bleed like a living organism. The process of turning a kyber crystal dark is called bleeding and involves forcing all the rage, anger, hate and pain into it using the dark side of the Force. This was explored in Marvel Comics stories as Darth Vader: The Chosen One.
In this comic book, when Darth Vader claimed the kyber crystal that powered the lightsaber of the Jedi Master Kirak Infil'a after killing him, he took the crystal to Mustafar, where in the confines of a heiroglyphed cave alive with the dark side of the Force, Vader bent the crystal to his will, holding it in his hand and forcing all his rage and pain into it, even as the crystal tried to return Vader to the light with visions of him becoming a Jedi once again. The crystal lost this contest of wills and eventually submitted to Vader as its new master, now and forever red with the dark side powering it. Similarly, in The Rise of Kylo Ren, after deciding to follow his path in the dark side and become Kylo Ren, Ben Solo transformed the kyber crystal of his old Jedi lightsaber by pouring all the hate and pain he felt about his family legacy into the crystal as he remembered the faces of his loved ones. Ben managed to bleed the crystal and turn it red, but it cracked during the process, which caused his lightsaber to become unstable.
Kyber crystals can be healed in this manner as well using the light side, but the resulting process does not restore their original color, turning them permanently white. It is likely that this process was utilized by Ahsoka Tano when she took her kyber crystals from the Sixth Brother and turned them white using the light side of the Force.
- Blue: Traditionally, the Jedi use blue-bladed lightsabers.
- Light Blue The Jedi rarely use light blue-bladed lightsabers.
- Green: Traditionally, the Jedi use green-bladed lightsabers.
- Yellow-Green: Ahsoka Tano once used a yellow-green lightsaber.
- Red: Traditionally, the Sith use red-bladed lightsabers. The red color was often achieved through infection by the dark side of the Force, which was known as "making the crystal bleed".
- Purple: The Jedi rarely use purple-bladed lightsabers.
- Yellow: While the Jedi rarely use yellow-bladed lightsabers, the Jedi Temple Guards often use them. Rey currently uses a yellow-bladed lightsaber. Asajj Ventress also owned a yellow-bladed lightsaber until her death by Count Dooku.
- Black: Tarre Vizsla is the only known Force-user to create the one-of-a-kind lightsaber called the Darksaber.
- White: The Jedi rarely use white-bladed lightsabers; although Ahsoka had them as her second lightsaber set. White blades usually were a result of healing a kyber crystal infected with the dark side of the Force.