Lycaon

Lycaon is the first werewolf.

History
Lycaon was once a mortal king of Arcadia, son of Pelasgus and Meliboea. He tested Zeus, who was a guest, by serving him human meat. He also ordered people to murder Zeus while he slept, to test his immortality. Zeus became angry as a result of his actions. As punishment, he turned Lycaon into a wolfman and killed all of his fifty sons with lightning bolts. 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.

The Lost Hero
Jason Grace, Piper McLean and Leo Valdez met Lycaon while they were searching for the home of Aeolus. He was ordered to kill them, except for Jason, who he is ordered to kidnap. 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. He says that imperial gold, celestial bronze, and mortal steel cannot harm him. Piper then realizes that since lycanthropes can be injured by silver and 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 shows her true, godly form.

Abilities
Being a lycanthrope, Lycaon is not only immortal, but also immune to any weapon that isn't made of silver, even magical ones like Imperial gold and Celestial bronze that's 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 wolf's leader. However, Lycaon isn't truly indestructible as (was cited before) he can be slain by silver (even if not permanently if he reforms), harmed by fire and is susceptible to divine power. He also has great reflexes, being able to catch an arrow in mid-air.