The SOL-9000 is a large spherical computer that contains the digital versions of eight members of the Gazel Ministry. They were put there by Krelian. You see them as blue and red faces in the "fishbowl-like" ship throughout the game.
After the death of the Gazel Ministry members 500 years prior to </span>Xenogears Episode V, this machine was constructed to hold their data and personalities. The SOL-9000 was the only machine that could activate the Gaetia Key. Krelian slowly erased the Gazel Ministry from the SOL-9000 after the Gaetia Key was used and the digitalized Gazel Ministry had expired their use. This also gave Krelian complete control over -Project Noah- and a chance to begin the Ark Plan.