This is the legend of King's Quest...

Once, in a kingdom called Daventry, there lived a King named Edward.  Daventry was a very old kingdom, and it had its share of kings, both good and bad, over the thousands of years. King Edward was a very good King, but he was also very old, and without children. Disorder ruled the land since the loss of the Three Great Treasures. King Edward feared that disorder might degenerate further once he died. Besides, he knew (as well did his people) that without an heir to the throne the kingdom would be in dire straits indeed. Thus, King Edward sent for his favorite knight, Sir Graham.