Very nice! I really like both Bastra and Bringen, especially the waterfall.
Although it raises some questions. Will you be able to settle near water and be able to build your own naval force in sort of dockyard, or do you have to purchase them from minor NPC cities in the vicinity of water?
And on a second note, the rock net is a nice idea. I myself had something of a similar idea for orcish siege defense: The Warg Pole. It's basicly a few wargs leashed to a pole which can be build outside the walls and released when enemies approach, attacking the nearest units. Merely suggesting