This game sounds awesome but the great unsolved game feature in these sort of games involves zerging for territory control. So will post-prelude territory control be siege based (towns can only be sieged at certain times) or economic strangulation based? The siege strategy is the common one yet economic strangulation might solve a lot of problems.
The mention of the impenetrable mist at the edge of the settled lands got me thinking that this would be a good idea for protecting tribal territories by nerfing all enemy characters who would also be the only ones to see the mist. This mist would have to be maintained by economic activity making crafters as important as PvPers in tribal defense. This mist would be strongest at the town center.
The mist would be generated from all tribal buildings so an enemy force would have to destroy various out-buildings first in order to weaken the mist and then work its way towards attacking the town center. With the mist having a slow decay rate a tribe will not wake up one morning to find its city gone unless the territory had been attenuated over weeks of attacks. This would also tend to disperse attacks making them more raid-like instead of one big laggy zerg fest.