I might be blind, I might even be stupid, but I can´t for the life of me figure out where in Nirmathas, the village of Kassen is located. It should be on the Tourondel River, but I can´t find that one either, so am I just blind or have I just missed them.
Their not on the map, because their quite small.
But the Tourendel is the river west of Vellumis, running through the fangwood on the lastwall/nirmathas border. Kassen is somewhere near where it turns down towards Skelt by it's description.
In most cases, a settlement smaller than a "small city" won't appear on the poster map unless there's something VERY unusual about that location. There are villages all over the place, and putting them all on the poster map would make it so cluttered that it would be almost useless. It also makes it easier for you to place it where you need it for your campaign.
Also, see the thread under the product listing for Crypt of the Everflame. There's some good discussion there about where it is (although the info from v-p gives you a good idea). /salute!