Rick Riordan
12) The burning maze
13) The red pyramid
All year the half-bloods have been preparing for battle against the Titans, knowing the odds of victory are grim. Krono's army is stronger than ever, and with every god and half-blood he recruits, the evil Titan's power only grows. While the Olympians struggle to contain the rampaging monster Typhon, Kronos begins his advance on New York City, where Mount Olympus stands virtually unguarded. Now it's up to Percy Jackson and an army of young demigods
...In this adventure, Annabeth encounters more oddities in the subway than usual, including a two-headed monster and a younger blond girl who reminds her a little of herself. This is the story fans have asked for, in which Annabeth Chase teams up with Sadie Kane. The demigod daughter of Athena and the young magician from Brooklyn House take on a larger-than-life foe from the ancient world. Perhaps even more disturbing than the power-hungry god they
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