Leaving Korrinth, Don knew he's leaving a few loose ends but since he and his men were not ready to take on the Cold Moon Palace, he had to leave without tying those loose ends.
It was only Don's concern because after killing the Agorians if he also conquered Korrinth by killing their army, he wouldn't have enough men to protect the kingdoms which could make them vulnerable to many outside powers.
So now he could focus on building his army without worrying about anything for a while.
The kingdom of Agoria, terminated to the north-east by a ridge of miles high mountains, which were altogether impassable because of the volcanoes upon the tops. On the three other sides, it was bounded by the ocean. There was not one seaport in the whole kingdom since the coast was so full of pointed rocks, and the sea generally so rough that there was no venturing with small boats.
So in other words, Agorians had little to no income from their seas.
