Daughter of Poseidon
She is one of the most powerful half-bloods of the century - meet Anya Imeson, daughter of Poseidon, blessed by Artemis. After running away from home, she meets Luke, Annabeth and Thalia, and joins them for a few bittersweet months. All is well, until one fateful night when she sacrifices herself to save her friends, but is saved by the sea herself afterwards. When she turns up at Camp Half blood a while later, little does she know how much danger she is in, or how much she will cause . . .
(A 'Percy Jackson' fanfic, contains spoilers as many do.)