Riordan draws heavily upon the trope of the hero’s journey, and it becomes a central theme of the novel. The hero’s journey is a common trope in literature and often appears in Greek mythology. In narratology, Joseph Campbell examines the hero’s journey as a prototypical path the hero undertakes throughout a story. Although Campbell describes 17 individual stages, the hero generally goes on an adventure, wins a victory in a decisive crisis, and returns transformed.

Much of Percy’s character trajectory mimics this journey. At the beginning of the book is the call to adventure, when the Oracle reveals the Great Prophecy that Percy and everyone else assume applies to him. It ends with the promise: “A single choice shall end his days, Olympus to preserve” (55). Next there is the refusal of the call, in which Percy debates whether or not he wants to take on the duties of the Prophecy. Following that is the meeting with the mentor, and for Percy this is Chiron. His mentor gives him advice and guidance that will help him on his way.

Percy enters the next stage when he embarks on his adventure and is on the road of trials.