A daughter of Athena and Percy's closest companion and eventual partner. Brilliant, driven, and deeply competitive, she has been training at Camp Half-Blood since she was seven. Her fatal flaw is hubris - she believes she can do anything. Her arc through the series is about learning that intelligence alone is not enough and that asking for help is not weakness.

God of the sun, music, poetry, and prophecy. Protagonist of the Trials of Apollo series in which Zeus strips him of his godhood and sends him to earth as the awkward mortal teenager Lester Papadopoulos. His arc across five books is a genuine redemption story - he begins as an insufferable narcissist and earns his way back to godhood by learning what it costs to actually care about someone.

A fourteen-year-old who discovers he is a host for the god Horus and a descendant of two pharaohs. Raised travelling the world with his father, he has no fixed home and no friends until the events of The Red Pyramid.

A son of Mars - the Roman aspect of Ares - with the ability to transform into any animal. Descendant of Poseidon through the Chinese demigod tradition. His life is literally tied to a piece of firewood. One of the most genuinely kind characters in the Riordanverse.

A daughter of Pluto - the Roman aspect of Hades - and one of three Roman heroes given the prophecy that opens The Son of Neptune. Quiet, watchful, and carrying a past she rarely talks about, Hazel can sense and control precious metals and gems underground - a gift she finds as much a burden as an advantage. She fights alongside Frank Zhang in the Fifth Cohort at Camp Jupiter.

A son of Jupiter - the Roman aspect of Zeus - and praetor of Camp Jupiter. Wakes at the start of The Lost Hero with his memory erased. His arc through Heroes of Olympus is about the tension between Greek and Roman identity and what it means to lead. Thalia Grace's younger brother.

A son of Hephaestus with the rare ability to generate and control fire. The comic relief of the Heroes of Olympus ensemble who turns out to be carrying more grief than he lets anyone see, particularly when it comes to his mother and the workshop fire that took her.

A son of Frey, Norse god of summer, who dies on his sixteenth birthday and wakes up in Valhalla. Annabeth Chase's cousin. His voice - wry, self-deprecating, and unexpectedly thoughtful - distinguishes him from every other Riordanverse narrator.

A daughter of Demeter with control over plants and seeds, assigned as Apollo's master when he is cast down to earth. Difficult, unpredictable, and deeply traumatised by her upbringing under Nero. Her relationship with Apollo is the emotional core of the Trials of Apollo series.

A son of Poseidon who discovers his divine heritage at age twelve when monsters begin attacking him. Over five books he grows from a confused kid who can breathe underwater into the demigod at the centre of the Great Prophecy. His fatal flaw is excessive personal loyalty - he would risk the world to save the people he loves. Continues as a major character through Heroes of Olympus and appears in later series.

A daughter of Aphrodite with the power of charmspeak - the ability to make people do what she says. Self-conscious about her heritage in a series where beauty and love magic are considered less impressive than combat powers. Her arc is about redefining what strength looks like.

Carter's younger sister, raised in London with their grandparents. A host for the goddess Isis and one of the most naturally talented magicians of her generation. Funnier and more impulsive than Carter, she narrates half the trilogy.

A son of Hermes and the primary antagonist of the original Percy Jackson series. His resentment of the gods who ignore and exploit their demigod children makes him the vector for Kronos's return. His arc ends with a redemption that the story earns.

A child of Loki with the ability to shapeshift between human forms and a gender identity that shifts accordingly. Alex uses he/him or she/her pronouns depending on the day. Prickly, lethal with a garrote, and one of the most distinctive characters Riordan has written.

A dwarf and son of Freya with an extraordinary gift for fashion and craftsmanship. One of Magnus's two companions from his mortal life. His sense of style and his skill with materials are not separate things - he makes weapons and armour of genuine power.

A satyr and Percy's best friend, assigned to protect him before either of them understood what Percy was. Deeply anxious and deeply loyal, Grover's great ambition is to find the lost god Pan. His empathy link with Percy becomes a recurring plot device across the series.

An elf and one of Magnus's two companions from his mortal life. Deaf, communicates in sign language. A rune magic practitioner of exceptional talent from a family that considered his deafness a source of shame.

A son of Hades who first appears as a cheerful ten-year-old obsessed with a card game and becomes one of the most powerful and isolated characters in the series. His arc across both the PJO and HoO series is about surviving grief, accepting his sexuality, and finding that belonging is possible even for someone who lives between worlds.

A mortal girl with the rare ability to see through the Mist - to perceive monsters, gods, and demigod conflicts that other mortals cannot. Perceptive, artistic, and unimpressed by the world of demigods until she is pulled into it through her chance encounters with Percy.

Praetor of Camp Jupiter and one of the most capable leaders in the series. Daughter of Bellona, Roman goddess of war. Her arc in Blood of Olympus is one of the series' best subplots.