Son of Chaos: A Story from the world of Percy Jackson

Erin de Martino is the only child and son of Eris, the goddess of Dischord, and for that he gets a reputation for being trouble at Camp Half-Blood. Just when he wants to mind his own business, he receives news that his mother's Golden Apple, which amplifies her power, was taken from her and split into four pieces, one of which with the core was gifted to him on a day he received his mail from the outside world. With a message from his mother, he is tasked to help Eris retrieve the other three pieces from Zeus, Hades, and Poseidon and restore the apple and return it to her. But when Percy, Annabeth, and Grover find out what he's up to, Erin must now race against them before they can get the pieces. Luckily he has her mother's gifts and pension for trickery and chaos.