Cavern of the Stolen Fayth
The Cavern of the Stolen Fayth is an optional side quest area that you can visit once you reach the Calm Lands. They can be accessed by taking the valley pathway after the team defeats Defender X along the bridge.
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The game does not require you to visit the Cavern of the Stolen Fayth, but the first time that you can access it is while traveling through the Calm Lands. Check out the Calm Lands section of the strategy guide for more information:
25) Calm Lands
Walkthrough Guide
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Arriving at the Calm Lands, exploring Remiem Temple for the first time, visiting the Monster Arena and completing the Chocobo Trainer side quests.
There are some side quests that can be completed in the Cavern. Namely, this is where you obtain the optional Aeon Yojimbo. Check out the side quest page for more information:
Cavern of the Stolen Fayth
Side Quests
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This side quest can be completed as soon as you reach the Calm Lands and is where you obtain the optional Aeon Yojimbo.