Complex sentence: Elli's story shows when she first discovers Mr. Pop, Alder's shows him learning what it takes to be a Bedoowan Knight, and Aja's features a competition between her and a classmate.
Split into simpler sentences: Elli's story shows when she first discovers Mr. Pop. Alder's shows him learning what it takes to be a Bedoowan Knight. And Aja's features a competition between her and a classmate.