The War of Night
Broken into three city states, the human population are at constant war with each other. Each is run differently and each believes that they are the best hope to push back the undead threat. See the City States below for more information on the specific nationality for each city.
To make this happen, they have minor wars to annex the smaller settlements between the Cities as a way of gathering power in the hopes of being able to move on a larger city further down the track. By uniting all the human cities, they would then become the pre-eminent power in the land and moving onto the elven, dwarven and gnomish cities would prove a more simple task.
Humans are the most numerous of the races. They build and grow at a rate the other races can not hope to match, but they have also forgotten more of the lands history and their own survival hinges more on the successes of the past in terms of runic defences on cities and settlements.
The Couriers are a small enclave in the human cities and not capable of large scale runes, so the human population must rely on the existing wards on the walls surrounding their cities.
Because their cities populations grow some much more rapidly than others, they have found a lack of space in all their major centres, and with no room to expand the existing cities, they must start to look for other places to start settlements.
Of the other races, the humans deal with the gnomes most of all. Trade between the humans and gnomes is strong, although subject to the occasional volatile set back. The dwarves are known to trade at times, but tend to stay safe behind their massive walls, content to let the humans implode. The elves, while not entirely xenophobic, struggle to understand the human need for expansion and have all but forbidden contact with the humans.