I didn't think the fortresses in the Fjords were too bad - more or less just tedious. I was a 23-25 working on Xanlosh (sp) and got 2 levels on his fortress alone. Had to go back to a previous save cuz I saved in a bad spot
Definitely have your creature and/or demon/undead and do NOT tell them you'll use your dragon form. That's where I messed up - I told him I was going to use my dragon form and immediately saved after the cutscene - I was massacred by the flying things he called in. One shot killed me. Over. And over. And over. heh.
Good luck!
