Levistone

The Levistone, also known as Floater Stone, is a key item in the original Final Fantasy. It is found in the Ice Cave, guarded by the Evil Eye. With the Levistone in their possession, the party can travel to the Ryukahn Desert, at which point an event is activated automatically as the Airship rises from the sands. The party can use the Airship from here on.

Dissidia Final Fantasy
The Levistone makes an appearance as a Trade Accessory in the game.