There are 3 teleporters in the cave with Barnabus, which you should explore before taking out Barnabus (you only need to do the 2 with the generators, but a couple people had problems getting the last door open in the highest area if they killed Barnabus first).
Back in the fjords, there is a bunker high in the mountains behind those anti-dragon shields and defenses. That is where you need to get to lower the barrier and disable the shields (there are a couple traders in there, as well, after they surrender).
You can either use a teleporter to get up there (the Camp Sentinel View teleporter, on the west side of the island in the middle of the channel, will bring you to Camp Eagle's Nest, where you can access the bunker) or it is also possible to fly above the anti-dragon shield and drop down in human form, if you find the right spot.
