I think this may be causing issues for the AI, but regardless, the monster spawn rate is just totally out of whack later in the game
Here's a very late game picture - this is with a Sovereign uber-stack that has 11+ movement for the entire stack, capable of killing ANY npc monster ai stack instantly in autoresolve
The monsters will literally spawn faster than I can kill them. This is true anywhere on the map that is outside nation influence borders.
I understand they want the 'wilderness' to be dangerous, but the current implementation is just absurd - if I kill 5-6 of those stacks you see to the right, another 5-6 will spawn ON TOP of my sovereign, right in line of sight!
I think this is also having negative effects on the AI, because if the AI falls behind and you ramp up the wilderness danger level, they can no longer safely expand/travel, unless they have the critical mass of strength necessary to 'trim the weeds' for placing a new settlement/running a caravan/exploring/going on offense.
