Random plotbunny time! If you're interested in developing this idea with me, shoot me a pm.
Dom mage/ sub prince
Long ago, a kingdom was taken over by a tyrannical sorceress. Witches, monsters, and warlocks wrecked havoc over the land until one day a great hero rose up and vanquished them one by one, finally killing the sorceress herself. The hero married the princess, and they become benevolent rulers and were beloved by their people. A few years later the king and queen announced the birth of their first child. It should have been the sort of story that happily ever afters are made of, but it wasn't to be.
During the nameday celebration of the infant prince, the mother of the sorceress placed a terrible curse upon the boy. Because the king had taken her daughter, she cursed his son to suffer and die horribly on his 21st birthday.
The people searched and searched for a cure but there was none to be found. The only sure way to break the spell is to kill the caster, but the witch had disappeared. With little more than a year left, the prince decides to go on one last quest. There had been rumors of a great white witch in the lands to the south, who's magic might be strong enough to break the spell. When he arrives, he finds that the witch has recently died. Her grandson, however, might be able to provide some answers.