Complex sentence: After several people who venture out onto the surface of Erythro are mentally damaged by the experience, the main character in the book, Marlene Insigna Fisher, is drawn to go out onto the surface.
Split into simpler sentences: After several people who venture out onto the surface of Erythro are mentally damaged by the experience. The main character in the book, Marlene Insigna Fisher, is drawn to go out onto the surface.