Coriana VI was a low-tech planet, noted for being the location of the final battle of the Shadow war, departure point of all the remaining First Ones, including the Vorlons and Shadows, from the galaxy as well as the last known location of John Sheridan before he disappeared with Lorien beyond the Rim in 2281.
During the War, The Shadows forced the natives of Coriana VI to allow a base on their planet and when the Vorlons began deploying their planetkillers, Coriana VI was one of the worlds targeted. The planet was saved when a group of First Ones, including the Walkers of Sigma-957 destroyed the planet killer before it could move in range. As a result, the Vorlon Fleet called in all of their other ships, an event which in turn saved other worlds, such as Centauri Prime, which had also been targeted, only to have the Planetkiller turn back at the last second.
Coriana VI system was also the place where Sheridan passed "beyond the Rim" at the end of his life.