Enhanced by a Force-boosting crystal, fires a blast of Kinetite

The duel was furious, and carried Vader and Skywalker through the temple to a chamber where there was a dark circular opening in the floor, the mouth of a deep pit. As the battle wore on, Vader found himself breathing hard through his respirator. But then, thanks to his proximity to the Force-enhancing Kaiburr Crystal, he felt a sudden surge of the power of the dark side, allowing him to project lightning from his fingertips for the first time in his life. He hurled Force-energized lightning at Skywalker, but his young opponent deflected the blast.

The Rise and Fall of Darth Vader, Chapter 17, Page 170