This map shows the four Empires at their height, just as the Wars between the Empires broke out.
In the Northeast is Toutus, the yellow border showing the extent claimed (not necessarily controlled) by the empire.
In the Northwest is Bursia with the red border
In the Southeast is Bellenos with the magenta pink border.
In the Southwest is Telthus, which has not been described yet. I'm thinking about leaving this only outlined for anyone else to fill in.
The areas already detailed in this blog (the Kingdom of Teiglin, the Godsblood Straits and Walrus Freehold) are in the boxed areas on the west coast of Toutus.
In the south of Bellenos there is the region that contains Tekhumis the Desert Port.
As can be seen from the map, the Empires, though great, did not cover the whole of the surface of Kaelaross - large areas are unclaimed. Some of this is uninhabitable wilderness, others dominated by barbarian tribes and a few places there are small, independent realms that refused to be dominated by any of the four empires.