|“||Oh, we've been patrolling for you all across the west, demigod, hoping we'd be the first to find you. The giant king will reward me well when he rises. I am Lycaon, king of the wolves. And my pack is hungry.||”|
Lycaon was once a human king of Arcadia, the son of Pelasgus and Meliboea. He tested Zeus, who was a guest, by serving him human meat, including meat from one of his own sons. He also ordered assassins to attack Zeus while he slept to test his immortality.
Zeus became angry as a result of his actions, and punished Lycaon in the manner which, after Otis and Ephialtes had made an attempt to assail Olympus, he related thus to an assembly of gods: when they had all sat down in their marble recesses, with the highest of them in his place, supported by an ivory scepter, he struck his terrible head thrice or four times, which moved the land, sea, and stars, saying: "The human race must be destroyed: I swear on the infernal flood that flows through the Stygian grove under the earth! Everything should be tried, but that part of the body which cannot be cured must be hewn off by a sword, lest the healthy part be lost as well. I have still demigods, nymphs (the rustic gods), fauns, satyrs, and silvan mountain-dwellers; whom, since we deem them not yet worthy of the honor of heaven, let us let live in the lands we have given. O gods, do you really believe they will be safe enough from me, who hold the lightning-bolts and reign over you, for whom Lycaon, infamous for his brutality, devised most foul trickery?"
Zeus had gone down to earth disguised as a mortal, and had come to the halls of Lycaon in Arcadia. When he announced himself to be a god, the people instantly began to pray. Lycaon, however, mocked their pious prayer, and then said: "I will test whether this be a god or man, nor will the truth be doubtful." That night, he devised a way to test him, weighed down by sleep, with unexpected death. Thus he was pleased. He then, with a knife, slit the throat of a hostage sent from the Molossian people, softened the half-dead limbs with scorching water, and cooked them with fire. Which as he placed them upon the banquet-table, Zeus recognized the slaughter and unroofed his halls with a vengeful flame. Frightened, he attempted to flee, but meeting the silence of the countryside, he let forth a shriek and tried vainly to speak. His face collected his rage and he was turned by the lust of his wonted slaughter into the livestock, and rejoiced again in blood. His clothes turned into hair, his arms into legs, and he became a wolf, keeping the traces of his old form: he had the same greyness and violence in his face, his eyes shone in the same way, and he had the same image of brutality.
Zeus also killed all of his fifty sons with lightning bolts, except Nyctimus, who was the slaughtered child. The Greeks named werewolves Lycanthropes after him, the first werewolf. It is hinted that Lupa has animosity towards him, since she is the mother of wolves.
For nearly a millennium, Lycaon remained immortal until he affiliated himself with Gaea, the goddess of Earth. He eventually encountered Jason Grace, Piper McLean, Leo Valdez, and Coach Hedge while they were searching for the home of Aeolus. He was ordered to kill them with the exception of Jason, whom he is ordered to kidnap under the request of Khione. Whilst preparing to attack Jason, Piper, Leo, and Coach Hedge, Jason attacks Lycaon but because Jason's sword is Imperial gold, the weapon does not even injure Lycaon but passes through him. He says that Imperial Gold, Celestial Bronze, and mortal steel cannot harm him. Piper then realizes that lycanthropes can be injured by silver and because Lycaon is the first lycanthrope, silver is the only thing that can harm him. When they realize that they have no silver, the Hunters of Artemis show up and attack Lycaon and his minions. He is injured by their silver arrows and so he flees. His wolves, however, appear at the Wolf House under the leadership of Khione, but they run away or are destroyed when Hera is released and transforms into her true godly form.
Lycaon is working for Orion. He tracks down Nico, Reyna, and Hedge in Évora, Portugal. Reyna pulls out a silver knife before Nico traps him and his wolves in bone. The three fight the wolves, aided by the fact that one of Reyna's hounds, Argentum, is made of silver which allows them to destroy the werewolves, turning them into pools of shadow. Lycaon breaks free and chases the trio to the Athena Parthenos where Nico has them climb the rope before he challenges Lycaon into jumping at him. Lycaon claws Nico's arms, but Nico stabs him in the heart with Reyna's silver pocketknife, killing him. Lycaon's eyes roll back in his head and he dissolves into a pool of inky darkness that Nico uses to shadow travel himself, his companions and the statue away.
His hair was greasy and ragged, the color of fireplace soot, topped with a crown of what looked like finger bones. His robes were tattered fur - wolf, rabbit, raccoon, deer, and several others. The furs didn’t look cured, and from the smell, they weren’t very fresh. His frame was lithe and muscular, like a distance runner’s. He had pale skin pulled tight over his skull. His teeth were sharpened like fangs. His eyes glowed bright red like the wolves. He retained the red eyes in his wolf form but had black fur and was almost as tall as a horse.
Being a lycanthrope, Lycaon is not only immortal, but also immune to any weapon that is not made of silver, even magical ones, like Imperial Gold and Celestial Bronze, that are usually capable to harm even gods. Also, being the first lycanthrope not only makes Lycaon the most powerful of his species, but also makes him the leader of them, a thing that might explain his rivalry with Lupa, the wolves' leader. However, Lycaon is not truly indestructible as (was cited before) he can easily be injured by silver, harmed by fire and is susceptible to divine power. He also has great reflexes, being able to catch an arrow in mid-air. He is very amazing, yet a bad enemy.
- It is unknown if Lycaon is immune to Stygian Iron, a magical metal from the Underworld that can absorb a monster's essence.
- His daughter Callisto was a Hunter of Artemis and turned into a bear by the goddess.