Complex sentence: In this world, Satan is her master, as she acts of violence and blasphemy mount, Maria realizes that she has been chosen by the Devil himself to destroy the convent and lead her sister nuns into hell.
Split into simpler sentences: In this world the Satan is her lord, she acts of violence and blasphemy mount. Sister Maria realizes that she is elected by the Devil himself to destroy the convent and lead her sister nuns into hell.