Last Child of the Sea

Camp Half-Blood is under attack. Despite the defeat of the Triumvirate, Camp Jupiter has been destroyed and New Rome is a mess. Many refugees have fled to the Greeks but even so, they are not safe. And quite frankly, their world has never been so close to discovery by the mortal world.
Percy Jackson, greatest leader of the Greeks and the Romans, leads and rallies the resistance against threats, monstrous and mortal, but even so, they know they are out of time. Olympus is failing, and soon the Heart of the Flame will shift- or disappear.
After his supposed death, Jason Grace wakes up in a stark-white room, like in those movies. He's been saved by someone and every instinct is telling him he KNOWS this guy only he doesn't. He has no choice but to trust him and play along, with him and a group of individuals who come from different pantheons and keep everything clear from each other.
Piper McLean is in Greece, or Crete to be precise. Why, she doesn't understand, only she's mourning the loss of the man she loves- or so she thinks. But she has a mission, and she doesn't know who she's supposed to be meeting or why they're important. The only hope everyone has, is the Prophecy appearing, something about hem only being safe when the Last Child of the Sea- the final offspring of the god Poseidon- appears in camp.