Nathaniel Moorhead is one of the Ten Pirates of Hawkins, and had one piece of the Treasure Map of Hawkins, which is needed in Ultima VI.
Moorhead died prior to Ultima VI, after living the life of a honest man at Empath Abbey, and the locket with the map piece was stolen from his widow, Sylaina, by Arturos of the gypsies. The Avatar had to buy the locket from them to get the map piece.