As we all know, one of the core gameplay elements in EWoM is the spellsystem. I really like the idea of destroying whole cities -for example- with a single spell [or let's call it ritual], however, there must be a way to defend against it. First of all, there must be spells which will protect the cities against the most dangerous spells like raise volcano, firestorm etc. Secondly, there must be spells, which will protect the armies against various spells, or at least raise their [magical] resistance against specific elements. [Example: Mass fire shield, mass ice shield etc.]

Without these protection based spells the late game will be all about casting devastating spells -> military action won't be very important. This way the spellsystem will be balanced enough.