A key item received in Oeilvert. A mysterious item Kuja is after.
It must be a magic-controlling device, but the technology is completely out of this world.
The Gulug Stone is a magic-controlling device in Final Fantasy IX that was placed in Oeilvert, and is possibly responsible for the anti-magic field in effect there. The stone is most likely of Terran design seeing that it is triangular, as is the middle of the recurring Terran emblem seen in many places associated with the planet, although Terra's Chronicles admit its technology is "out of this world." It is blue like Gaia's crystal and moon; red, like Terra's crystal and moon, and green, possibly representing an unknown party. Alexandria Castle's chapel, possibly as a remnant from the summoner tribe that had settled on the Mist Continent, has a red and blue design that resembles the Gulug Stone behind the dais. In the Android/iOS version of the game, the Gulug Stone is shown to have a purple eye in its centre, a design feature of many Terran technologies.
Kuja sends Zidane to Oeilvert to retrieve the stone so that he could enter Mount Gulug. When the player first gains access to the Blue Narciss, they can go to Esto Gaza, and if they try to reach Mount Gulug the way is blocked by a door that has a seal shaped like the Gulug Stone.