Ajna's Inner Realm, a term first coined in-game by Dhar, is a world that seems to exist within Ajna's mind. She is able to "access" it by meditating, and it is where Incarnations she absorbs generally reside for most of the story.
Beginning as a single floating island situated above ethereal clouds and under a starry sky, containing nothing but the ruins of a temple bell, the land grows as Ajna gains more comrades, and even seems to develop depending on the tastes, wants and/or needs of the Incarnations.