Grievous's castle was the personal retreat of the cyborg Supreme Commander of the Confederacy of Independent Systems, General Grievous. Located on the third moon of the Outer Rim world of Vassek, the castle was built into the rockface of a large gorge. Shrouded by the moon's heavy fog, Grievous's castle was specifically designed to cater to the needs of the general, with an operating and repair room, a hangar for his starfighter, and several booby traps intended for intruders. Aside from Grievous, the castle was the home to the general's repair droid EV-A4-D, Gor, Grievous's pet roggwart, and a cadre of IG-100 MagnaGuards who protected the lair.