 While every Other may enter the first level, only the most powerful ones can get as far as the fifth, and the select few can get through to the sixth.While the first levels are unpleasant and devoid of life (apart from blue moss in the first level), fifth and sixth levels are quite hospitable, with life and vegetation.The main mystery of the final novel is what is on the seventh level- only the greatest of magicians can penetrate to the seventh level.