Rise of the Obyriths
Caladan is the name of a plane on which Arcadia is located. Caladan is essentially a water world, with one small continent, which shares the name with the plane. Although there are numerous islands on Caladan, many are either uninhabitable or considered too small to maintain a large population.
In addition to Arcadia, the four other main kingdoms that Laconia, Aria, Corrin, and Byzaine.