Complex sentence: Within the world of the school, the heroines' adventures, which may end in near-disaster, but the fact do not, act to reassure the reader that the imaginary world is a safe one.
Split into simpler sentences: Within the world of the school, the heroines' adventures are not dangerous. Adventures, which end in near-disaster, but the fact that they do not acts to reassure the reader that the imaginary world is a safe one.