Phineas

"Oh, go talk among yourselves. I don't care. Just remember that without my help, your quest will fail. And everyone you love in the world will dies. Now off with you! Bring me a harpy!"

- Phineas in The Son of Neptune

Phineas is a Roman demigod son of Neptune with the gift of prophecy to see the future. Even though he is able to see the future, he is still a blind man.

History
Phineas is a demigod son of Neptune who lived in the city of Salmydessus, on the Black Sea with his two children and his wife (until her death). Phineas was able to see the future, as he had the power of prophecy. He would tell people of things the gods were planning, causing Zeus to become enraged. As punishment, Zeus caused Phineas to become blind and placed him on an island with a buffet of food. However, whenever he would try to eat the food, harpies would swoop down and take the food from him. He was forced to face this punishment until Jason and the Argonauts arrived on his island and sent the Boreads after the harpies, but spared their lives as a favor to Iris, the rainbow goddess. In return for their deeds, Phineas told the Argonauts how to pass the Symplegades; rocks that would randomly crash together and kill anyone trying to get past them.

The Son of Neptune
He is a blind son of Neptune that Gaea brought back to life and lived in Portland, Oregon. In contrast with his former life, Phineas was able to eat whatever he wanted, but the harpies that tormented him were cursed to only be able to eat the food from his table. Using a motor-powered weed hacker, he managed to starve the harpies into perpetual suffering because the Doors of Death were open and they could no longer die.

When Percy Jackson and his friends asked him for information, he told them that he will only give it to them in exchange for one of the harpies, Ella, whom he claimed was problematic, but in actuality, it was because Ella had vast amounts of information.

Percy, feeling sympathetic for Ella, befriended her instead. In order to get the information, Percy made a deal with Phineas, the deal involving the both of them drinking from two bottles of Gorgon blood. One bottle will kill the person that drinks it, while the other will cure any illness the person may have, including Phineas' blindness and Percy's amnesia. Phineas accepted the terms of the agreement and wrote the information on a scroll and placed it in his robes so that even if he picks wrong, he would still be able to give Percy the information he wants. While at first it appears he picks right, as his sight begins to return while Percy begins to experience pain, it turns out that Gaea influenced him to pick incorrectly. Phineas slowly began to turn to dust as he tried to find the information in his robes so he can destroy it before Percy can get it, but dies before he can find it. Moments before he dies, he claims that Percy will have a hard choice to make and he will make the wrong one.

Abilities

 * Phineas has the power of prophecy, since he is able to see the future. This ability is limited to major events, as he is unable to see events of chance or coincidence.

Trivia

 * Vincent Martella made a guest appearance during the day of Olympian Week that Phineas was revealed to be in The Son of Neptune. Vincent Martella does the voice of the character Phineas from the cartoon Phineas and Ferb.
 * He is the only known descendant or child of Neptune to be able to predict the future accurately.
 * Phineas in the book calls himself a son of Neptune, but in mythology his godly parent is Poseidon. This might be because he was in front of Roman demigods (other than Percy, but he thought he was Roman).