Percy was 7 years old when is mother, Sally Jackson had been killed by the Minotaur. He runs and encounters the Hunters of Artemis. They take care of him and train him to be the best warrior. At age 7, he has been given immortality. At age 19, he stopped growing due to the immortality. It has then been decided by Zeus that he has to be married to Artemis to prevent a great evil from rising.