All Darka needs for winning this war(winning as in CE will just be banging its head against a wall without getting any harm done to Darka) is one or two CE allies to stop bother coming up north. That or even a single decent sized realm joining in on the defense.
Since none of those realms have anything remotely interesting going on anywhere else in terms of wars they can join, good luck
Your best hope is that a war breaks out in the southeast, which could easily distract any or all of Suville, Tara, Strombran or even CE itself.