The Elsdon Duchy was the first territory settled when the first colonists from Welos arrived on the shores of the Nordahrian continent. It is located on the eastern end of Ansgar, at the base of the Elsdon Channel.

The Duke of Ansgar is also, traditionally, the King or Crown Prince of Ansgar. When the Crown Prince reaches adulthood, he is granted the Elsdon Duchy as his own in order to learn how to rule a territory and prepare him for the crown. 

The Elsdon Duchy is largely urbanized, home to Ansgar's largest city, Aetheston and several smaller towns. A large percentage of the territory is owned directly by the Duke of Elsdon and rented out to citizens. Much of the privately owned land in the Elsdon Duchy is held by other nobles of Ansgar (especially nobles from Eastern and Central Ansgar, who have built estates and villas.

The Duchy's major industry is import and export shipping and warehousing, followed by ship construction at the largest shipyards in Ansgar.