In The Interior Castle, Carmelite nun, mystic and patron saint of Spain Teresa of A?vila uses the metaphor of a giant crystal castle to explain her theory of the soul and the various stages it passes through as it progresses towards God. Beginning in the outer rooms, where demons are fought and vices are purged, the soul must reach the inner chambers, where it will enter betrothal and intimate union with God. Prayer is central to the journey, as the soul is guided by its practice and each phase represents a different category of devotion. Originally written as counsel for the sisters in her convent, The Interior Castle is a poignant and poetic reflection on prayer, humility and self- knowledge, and the path towards a deeper communion with God.