With his blond hair, sky-blue eyes, and tall, muscular physique, Jason Grace, son of Jupiter—the Roman aspect of the Greek god Zeus—is classically handsome. A small scar on his upper lip, made when he tried to taste a stapler as a youngster, saves him from unapproachable perfection. The inside of his right forearm bears the tattoo of an eagle with the letters SPQR and twelve slashes, one for each year he was at Camp Jupiter. His hair was once cut short but grew out during his time at Camp Half-Blood; it now has a groove cut through it, courtesy of a Celestial bronze bullet shot from the demigod Sciron’s gun. Jason wears Imperial gold-rimmed glasses to correct nearsightedness. IVLIVS, an Imperial gold coin that turned into a sword or spear—heads for the sword, tails for the spear—was replaced by a Roman gladius after it was destroyed in a fight with the giant Enceladus.

Jason has a good sense of humor, though that side of his personality is often overshadowed by his serious, sometimes sad demeanor. His friends know him to be kind, gentle, and trustworthy—and his enemies soon learn that he will stop at nothing if his friends are in danger. He has superhuman strength and agility, lightning-quick reflexes, and impressive sword, spear, and hand-to-hand-combat skills. As the son of the god of sky and weather, he can generate storms, fly by summoning the power of wind, and control lightning.

But while Jason appears to be all-powerful and mentally strong, he is not impervious to injury and internal turmoil. He struggles to choose which camp to align with, Camp Half-Blood or Camp Jupiter. When the ghost of his enemy Michael Varus stabs him, the wound festers until he finds a way to unite the camps by accepting the title of Pontifex Maximus, high priest of Camp Jupiter, but deciding to live at Camp Half-Blood.