If you have a PC/NPC or are in charge of building for, or running a city please feel free to take a look at the notes I wrote for players who have spent extended periods there and apply them through RP or to any quests you might have going on.
Also, should you see a player who has been in a city with a weakness attached (elmensfaar, nherazkar, etc), and they are doing strenuous things (fighting hordes of mobs, trying to climb a wall to get away from combat, etc), feel free to inform them that exersion has caused their penalties to extend by a further 1 or two, depending, should they succeed their climb/tie check, etc.
Also, don't feel that because the cities are suffering, it is a constant thing. The global effects and downtime attacks are just that, things that are happening from time to time (some more constant than others), but not constantly. It is basically to add flavour and get people thinking about things, please do carry on with what you have in mind there and continue without hindrance.
The weaknesses and penalties will not apply to 'everyone' in the city, of course. A prince might be tired of all the whining but he'll generally be good, where as a warrior will be assumedly fighting for his town and will be effed, a citizen will be level 1 commoner and will crap themselves every night resulting in fatigue, etc. The stone minded monk might not suffer quite as much as everyone else, but don't assume that because they're a monk, or they're a mage with ninty will, that they're immune. Yes, it will have a lesser effect on one with an iron mind, but enough heat will make iron melt, enough cold makes it brittle, and so forth.
If you are interested in taking this and putting a spin on it, and working with it then feel free to run some random encounters with lesser undead, no more than CR 2 monsters. From time to time you may wish to throw in some sentience, in which case it should be a necromancer of no more than CR 7 and able to cast nothing above level 3. The necromancers will know nothing, of course. They are just innitiates who are being used to persuade the undead in the right direction and ensure they pressurise the world.
Do not over-do the necromancers. They are rare encounters.Should you wish to apply some cock-and-ball story to the necromancer you may have spawned, then do feel free to spin something, perhaps they have been told something by some one knowing that they will spill the beans under enough pressure to lead the players away from the truth and away from the ultimate goal.
I will not post the plot here, of course, but I will give everyone freedom to throw things around. No 'special' undead of yet, though. If you -really- need to be exotic, throw a ghoul in amongst the skeletons and zombies.
As well as the above you're totally free to run some subplots and be inspired by this when it comes to your city, perhaps have people investigate why the crops are failing, send some one out to find a missing scout, have some one venture into the tundras and investigate trade routes, anything you might happen to conjure up.
Creaturepaedia:Solinar:Zombie (CR1)
Skeleton (CR1)
NherazkarZombie (CR1)
Skeleton (CR1)
Tundra Drake (CR 10(ish)), Custom - Dragons - Tundra Drake, Tundra Wyrmling
WestportZombie (CR 1)
Skeleton (CR1)
Undead Lizardman (CR no more than 5)
CrossroadsZombie (CR1)
Skeleton (CR1)
Undead Animal (CR no more than 5)
ElmensfaarElven Zombie (CR1)
Elven Skeleton (CR1)
Undead Coshee (no more than CR5)
RivenwoodNo undead presence of yet. Will update.
ZheradanNote: Very rare spawn chance.
Undead Giant Bug (CR no more than 5)
Rotting Zombie (CR 1 or 2)
Undead Jungle Animal (CR no more than 5)
MorinsenZombie Dwarf (CR1)
Skeletal Dwarf (CR1)
Decrepit Spawn (CR no more than 5)
GluckweiglNo undead presence of yet. Will update
That Desert Place that I can't spell, everSkeleton (CR1)
Rotting Zombie (CR1 or 2)
_________________
Never under estimate the power that language imparts. Sticks and stones may break your bones, but words can break hearts.