Grand Shario was the flagship of OZ Prize, and served as it's mobile base of operations. The Stardust Knights and other elite pilots operated out of it during OZ Prize's siege of MO-V.
It was eventually destroyed when a dying Dr. Berg activated a program to crash it into the Earth after destroying everything in it's path, including MO-V, and the combined power of the G-UNIT Gundams channeled through OZ-19MASX Gundam Griepe allowed them to destroy it before it could obliterate the colony.