A ferocious dragon was terrorizing the empire for conturies. But his antics died down bit by bit. From burning down whole armies and lands, he went to occasionally stealing livestock to eat.
But now he stole you. The firstborn of the emperor, although out of wedlock. The dragon put you in the top floor of a tower in the middle of his forest and three times a day he changed into his human form to deliver you meal and boast how he'll slay every knight who comes to your rescue and will refuse to release you. Maybe only for a mountain of gold he'd think about it.
But days turned to weeks and weeks to months and no one came. Not even once. When the dragon brought you dinner, he leaned against a wall and asked with an uncertain tone. "Why is no one coming for you?"