(A/N: Spoilers!!! Do not read unless you've read the entirety of Blood of Olympus) 

Percy held a sobbing Annabeth in his arms as they staggered up Half-Blood Hill. He couldn't be dead. Leo was immune to fire. Even if he had found a way to get the physicians cure in him, the blast would have surely killed him and destroyed the vial and Festus (again). "Brother?" A voice called. "Tyson," Percy whispered. Tyson beamed and hugged Percy and Annabeth ridiculously tight. "Where is Fire-Boy?" He asked happily. "He's dead Tyson." Percy whispered as Tyson's face fell and huge tears fell from his single eye. "I don't know if he's QUITE dead." A voice said. Percy jumped. "Geez, Nico!" Percy said loudly. "Don't sneak up on me like that." "I would feel something if he died. He's dead, but not quite dead." "Tyson!" A voice unfamiliar to Percy's ears called. Percy looked behind him and his heart pumped. This girl looked exactly like him. "Sister!" Tyson called. Percy hoped there was a mistake. Maybe she and Tyson shared a nature nymph as a mother. It could possible. But by the knowing look Chiron was giving him, Percy knew one thing. He had a sister, a daughter of Posiedon.