A Kyber Crystal was a Force-attuned crystal that the Jedi and some Sith (who prefer artificial synth crystals) used to power their Lightsabers. They were also used to power other weapons in the conflict centuries before the founding of the Galactic Republic.
A Kyber Crystal was involved in the creation of a Sith superweapon that also functioned as the Malachor Sith Temple, with a Holocron serving as its activation key. This superweapon posed such a threat that a massive Jedi offensive was launched against Malachor, resulting in the weapon malfunctioning and turning all life within a considerable radius to stone. This weapon would be destroyed thousands of years later due to a conflict between the Galactic Empire and the Rebellion.
Since the fall of the Republic and the Jedi Order, the Empire uncovered a Kyber Crystal fourteen years after the Clone Wars, but the Imperial Freighter that was transporting it was attacked and destroyed by the Ghost in an covert operation that involved infiltrating the Imperial Academy on Lothal to find the shipment of said Kyber Crystal, the rebels managed to detonate the Kyber Crystal which produced a powerful destructive shockwave, destroying everything in its surroundings. Later Ezra gained one in a Jedi temple on Lothal which he used to construct his own lightsaber.
Kyber Crystals are mainly blue and green, but colours such as purple and yellow can be found; the Jedi would often acquire them from the planet Ilum. The Sith and other dark side Force users were known to use the Force to corrupt the crystals, a process called "bleeding" which caused the the crystals to become red in color. In at least one instance, Ahsoka Tano was able to purify a pair of such crystals that had belonged to the Sixth Brother; they became white as a result. Kyber Crystals also have a relationship with the Force, which enables Jedi to sense when a crystal is meant for them; Ahsoka Tano has described such a sensation as "seeing a light" and "hearing music" imperceptible to anyone else.
Kyber Crystals serve to focus energy; in the case of a Lightsaber it produces the blade, influencing both the stability of the blade and its color. It can also be used as the focus for an energy weapon.
- "Trials of the Darksaber" (Mentioned only)