It appears that an Earth Kingdom was planned, but eventually not implemented. Each kingdom is ruled by a monarch who is capable of powerful magic. Sia's kingdom, Myriade, is separated from the elemental realms by the Snowy Mountain and located in the southern part of the continent.
Myriade's inhabitants appear well-versed in magic. The continent of Callyge is located in the northeast of the map and is the T'soas' and Onimen's headquarters. Seaports protect Callyge from attacks.