Percy Jackson, the 14-year-old protagonist and first-person narrator, is the demigod son of Poseidon and a mortal woman, Sally Jackson. Percy often cracks dry jokes. The humorous first-person voice illustrates Percy’s laidback nature and gives the narrative a friendly quality. Over the course of the book, Percy matures. After the summer’s quest exposes Percy to the deadly realities of being a half-blood, his views on his own mortality change as he confronts the probability that he and his friends may die in the war against Kronos.

As a son of Poseidon, Percy can manipulate water and speak telepathically to horses. When Percy first tries to summon water, he needs to concentrate “all [his] might on shutting off the force of the sea” (155) so it won’t spread out of his control. However, with practice, visualization becomes easier, and he saves Juniper’s tree from a forest fire without causing damage, displaying his powers’ growth.

Percy is brave and impulsive. He often finds himself acting before realizing he made the decision to act. This is partly due to his ADHD, which in the world of the novel gives half-bloods heightened battle instincts.