Captured a Kraxis city (not their last one), and Karavox somehow got trapped in that city rather than teleporting out like a boss. I couldn't attack him, but luckily for me, a nearby group of river skaths took care of that. I suspect he was still immobilised from his previous defeat, which may have something to do with it.

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So far in this game I have captured two Kraxis cities that happily co-existed with strong adjacent monster layers until the moment I stepped foot in the city, at which point my invading army was promptly attacked. Ophidians and river skaths. The next city on my path of destruction has a dragon chillin' a couple of tiles from it, just beyond the fog in the top right corner of the screen and well within the zone of control of the city. I think I will leave that city alone for the time being.

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Here's Karavox being eaten by skaths: