The Mark of Athena by Rick Riordan is the 3rd book in the Heroes of Olympus series. In this book, all 7 half-bloods (Percy, Annabeth, Leo, Jason, Piper, Hazel, and Frank) must fulfill the prophecy. Annabeth has to complete her quest that her mother gave her at the same time. This book was very good, intense, and had a terrible ending (it was a major cliffhanger, literally). Haha.
5 out of 5 stars.