Rise of the Titans — Kate O'Hearn

In order to save Olympus, Emily and her winged horse, Pegasus, venture to Hawaii -- and a Hawaiian volcano -- in this fifth book of an exciting series that puts a modern thrill into ancient mythology.

The ancient rivalry between the Olympians and the Titans has been rekindled. However, this time the Titans have a secret weapon -- a weapon that rivals the Flame of Olympus. The balance of power is tipped in Saturn's favor now that he has found his own Flame of Titus. Olympus is almost in his grasp! And just when the Olympians need Emily most, she finds her own grip on the flame weakening.

If Emily is going to save Olympus, she will have to save herself first. To do so, she and Pegasus must head to the Diamond Head volcano in Hawaii to track down the one thing that can rescue Olympus…but can they get there before the Titans or the CRU beat them to it?