The creativity within the Star Wars universe exists in no small part due to the constant evolution of ideas that make up the series. For example, the original designs for Chewbacca by Ralph McQuarrie did not appear in the film, but they are seen again with the character Zeb from Star Wars Rebels. Another example of this can be found in items that hold significant value in the universe. Although Star Wars fans know that Kyber crystals are typically used to power lightsabers, they once had another function. They even went by another name -- the Kaiburr crystal. But unlike the final iteration, this crystal worked to enhance Force users' powers rather above all else.
The term "Kyber" was first introduced in a draft of the original Star Wars film where the crystal was spelled "Kiber" and was designed to be a MacGuffin for the film that gave its users the power to control the Force. By the third draft, the "Kiber" crystal belonged to Obi-Wan Kenobi, and it was his mission to steal it from the Imperials. Although the object was a prominent factor even when Luke Skywalker went by Luke Starkiller, the crystal was ultimately scrapped to focus on the relationship between Luke and Darth Vader. However, while the crystal didn't make the final cut, the powerful artifact still appeared in the 1979 novelized sequel to A New Hope, Splinter of the Mind's Eye by Alan Dean Foster.
Splinter never reached canonization once The Empire Strikes Back hit theaters, but before the film was released, it served as a follow-up to the hit story and managed to resurrect older ideas from A New Hope's earliest drafts. The book follows Luke and Leia on their way to a Rebel meeting on the planet Mimban. But when they're stranded, they're forced to survive on an Imperial occupied planet. While investigating, the two meet a woman who senses Luke's connection to the Force. She then tasks the young heroes with finding the Kaiburr crystal, an ancient rock capable of amplifying a Force users' abilities "one thousand times over." The story quickly becomes a treasure hunt with Luke and Leia in a race against time to get the crystal before Darth Vader.
While the Kaiburr crystal can power lightsabers, its enhancements on Force users are where its true power lies. One of its most noticeable effects is its ability to give Force users the power to heal, similar to how Rey healed Ben Solo. It could also affect users of the Dark Side, but rather than using its powers to help others, it amplifies their internal use of the Force. For example, in Splinter of the Mind's Eye, Luke and Darth Vader have a duel that pushes the young Jedi to his limits. Part of why Vader was an even more formidable threat was due to the effects of the Kaiburr crystal. When given a jolt of energy, Vader could access powers his robotic systems would never allow, such as Force Lightning. However, he also lost control of himself in using its power as his willpower began to drain. And as a result of his lack of control, Luke overcame his father and defeated him.
The Kaiburr crystal may be incredibly powerful, but the farther it's taken away from its home in the Temple of Pomojema, the less powerful it's the crystal becomes. That being said, it is still able to power lightsabers, as it's simple to obtain a shard from the crystal. The Kaiburr crystal later appeared in other forms of Legends media through Star Wars: Knights of the Old Republic II: The Sith Lords and Star Wars: The Force Unleashed, where the crystals were used as powerful focusing tools to create powerful lightsabers. That being said, the main canon has since relied on the Kyber crystal as a power source that doesn't typically focus or amplify any Force abilities.
While no longer canon, Splinter of the Mind's Eye shows the beginnings of the series' most important themes. From the Kaiburr crystal alone, the story shows that, while beneficial, certain power can still corrupt and make even powerful enemies shadows of their former selves.