The Shimmering Island is an island located by Esto Gaza on the Lost Continent in Final Fantasy IX. Situated to the south of the Lost Continent, the Shimmering Island appears at first to be a collection of glaciers. It is revered as a holy place by the temple at Esto Gaza, as it glimmers mysteriously.
Entering the island as part of the story is a point of no return, as the world map will slightly change and some areas become inaccessible after. It is thus best to assure the party has picked up all treasures and has everything from the shops before going through.
Shimmering Island is a gateway between the world of Gaia and the world of Terra that exists inside it via a giant teleportation spell; though who set up the spell is not specified, it was likely Garland. According to the Final Fantasy IX Ultimania Shimmering Island began glowing 1800 years ago, marking its opening as the portal between the two worlds. This was the time the world's calendar began.
The light of the Shimmering Island is the radiance of the crystals emanating from the dimensional interval where Gaia and Terra are joined, and is the subject of religious faith for the inhabitants of Esto Gaza, who call it the "Spirit Road". Zidane calls it "the path that leads the souls to Terra". When the gate to Terra is open, the radiance is at its greatest.
Zidane's party obtains four elemental mirrors from Ipsen's Castle. Traveling all across Gaia, the Hilda Garde III drops off two party members at each elemental shrine, where the guardians of Terra make their abode. The four are living seals to the entrance to Terra, and after they are destroyed, the Shimmering Island reveals a glowing, multicolored portal with golden lights whizzing throigh it. The party may access the portal via the Hilda Garde III.
After Kuja destroys Terra, the gateway nested on the Shimmering Island closes, and it regains its former icy appearance.
Zidane's ultimate weapon
During the endgame, Zidane can get his Ultima Weapon by using a Dead Pepper at the place where the island used to be while riding Choco. Shimmering Island remains marked on the large map view, where the player must position themselves right at the center where the island is marked to find the treasure. There are no bubbles unlike in the other ocean treasures.
Behind the scenes
The opened Shimmering Island portal shifts between emitting white, purple, and blue hues in the PlayStation version, but no longer does so in subsequent releases.
When the Hilda Garde III enters the the proximity of the Shimmering Island, the teleportation field is in a distinctly triangular shape with a circle at its center, representing the seal of Terra . The Shimmering Island portal looks similar to Kuja's teleportation spell , only on a larger scale.