... Among them, only Letos was level 18 with a more or less decent army (enough for two enhanced Meteor Showers). Two of them had only one unit each. It seems Railag is on his way to his third town, although it's not visible yet.
Letos and his widespread plague slightly tired me out. I fought him a couple of times – it was tough, although I probably didn't have the best Railag build.
As for the paths to the castles, check above; there's an open map there...