Chapter 7: Mario Shoots the Moon
This location is secretly located on The Moon. The fortress also serves as the home to the X-Naut Legion and the Shadow Sirens. This is the place where Princess Peach was taken to. The last Crystal Star, the Crystal Star, is held here and Mario and his friends had to use the cannon in Fahr Outpost in order to reach this place and fight Lord Crump to get the Star. Grodus traveled between the Mushroom World and his fortress using a Teleportation Machine, which has one end located in his laboratories and the other end located in Rogueport Sewers. The base is also the home of TEC-XX, which is the main computer of the whole fortress. Also, after Mario gets the 6th Crystal Star, Grodus takes Princess Peach and leaves the Fortress (possibly giving it to Lord Crump) so he can go to the Palace of Shadow. After Mario successfully destroys Magnus Von Grapple 2.0, he gets the seventh Crystal Star. After that, the fortresses explodes and Mario is unable to go back until the Shadow Queen is defeated.