River of Oßlivion

2 book in series. Follows Daughter of Poseidon. All the demigods from the giant prophecy are stuck in Oblivia, the space under the labyrinth but above the underworld. One drop of the rivers hellish waters, and your soul is gone. The only way to retrieve it is at the center of Oblivia, at the magic spring. Not only that, but Oblivion monsters poison will do the same if even a scratch falls on you from their claws. So what happens when Cora saves Nico, and pays the price by losing her soul?