Castelin is both an island to the west of Valwyr, and a province of Valwyr. Castelin’s ruler is Prince Ansbach.
Castelin is also unique in that it contains one human city, one elven city, and one dwarven city, all of roughly the same population. These inhabitants are the descendants of the Rebellion, a group of humans, elves, and dwarves, who rebelled against the King at the time and attempted to make Castelin Island a free state. They failed, but the King took pity on them and allowed Castelin to become perhaps the most free province in the kingdom. They have their own Provincial Council, their own codified law system, and the Prince, unlike the rulers of the other provinces, does not have absolute power. He is, in effect, one member of the Council.
In this way, Castelin is far removed from the issues of Valwyr.