Annabeth was slipping and Percy dived to save her; something went wrong. On the surface, Annabeth leads the Seven, desperate to rescue him and unite the camps. Alone in Tartarus, Percy finds himself making harsher choices, discovering darker methods, unlocking deeper powers, tortured and fighting for his life. He swears he's still a good kid. Post MOA

Twins born of a broken oath, one to lead the life of a hero, the other to lead the life of a murderer. Champion of Susanoo and son of Poseidon, the younger brother's tale is one of sadness, and tragedy...and of vengeance, and blood.