Cave of the Gi
The Cave of the Gi is a location that you can reach from inside Cosmo Canyon. Bugenhagen takes your team in to the Cave (where you must have Ninaki/Red XIII in your party) in order to have Red XIII learn more about his past.
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The story of the game leads the team to Cosmo Canyon after they have left the Corel Prison and have traveled through Gongaga. The Cave of the Gi is a non-optional area that you must complete while in Cosmo Canyon. Check out the Cosmo Canyon walkthrough page for more details on how to navigate this dungeon.
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There are a number of items that you can pick up in this area and there is no way to re-enter the Cave of the Gi later on in the game, so make sure you grab them all:
The map below shows the location of the Cosmo Canyon (which is where you can find the Cave of the Gi) on the World Map:
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