From the Live Letter Q&A
"Amdapor is mentioned in the white mage job quest line as well as several other sidequests, but this is a city-state that existed near Camp Tranquil. I'm sure many of you have seen the gated area in the western part of Camp Tranquil, but there is an ancient city past these gates deep in the forest, and this will be the dungeon. Players will face a great evil linked to the fall of this civilization, so please look forward to this challenging new addition to Eorzea."

Great evil Hmmm? (=_=)