The guardian

It has been 15 years since Percy Jackson was killed. 15 years since he was banished from camp for a crime he didn't commit. 15 years since he was betrayed by the ones he loved. 14 years since he was proven innocent. 14 years since his loved ones nearly killed themselves with grief. 13 years since his loved ones were given immortality to make sure it never happened again.
MODERN DAY
Artemis and her hunters are defeated and about to be killed when the use their last chance. Artemis summons a dead warrior to save them and be their guardian, much to the reluctance of herself and her hunters. When the warrior comes out of the ground in green and black hood, vest, jacket and trousers. But the thing that catches the hunters' eyes is the black bow and quiver with 12 arrows on his back and the sword at his side.
The warrior is Percy Jackson. Sworn to protect the hunt until he dies. He remembers his betrayal. He keeps his identity a secret. Nobody must know, he tells himself nobody must know.