The Prophetic Moment by Donald Haynes

Seven years have passed. A spell has robbed Cormac of any memory of them. When the Princess calls him from Thanekeep and frees him from the enchantment, he is astounded to learn that he has become the Thane of Rivershome. He has no time to adjust to the news. Along with the Princess, he must immediately resume the quest. They must seek the only one who can explain the prophecy—an ancient, wrathful dragon legend says lives in a mountain cave somewhere far to the east.