I went googling around for this one and the closest description to my problem seems to be from a user with the same problem over on the Steam forum.
I've been tooling around Orobas Fjords, doing a little bit here and a little bit there and so on. 90% of what I encounter is too hard for me but if I can find that 10% that isn't, I do it and the rest gets a little bit more feasible... anyway, I've been everywhere I can, thanks to the barriers.
And I went to Camp Eagle Nest, and had a conversation with the male and female black ring, and they attacked me (like Black Ring does) and then I was immediately punted OUTSIDE of their little cliffside lair. There is now a barrier up across the doorway, preventing me from getting back in. I can't even climb the ladder anymore. I assumed this was intentional and went around, doing other stuff. At least a level and a half's worth of other stuff.
So I found myself horribly stuck, with nothing left I could do, and pulled some walkthroughs. It seems that I was supposed to be trapped INSIDE the aerie, as if for a boss fight. And the switches I need in order to continue the game past this point appear to be in there as well. Where I am not. Short of going back to a two- or three-day old save that will set me back so far I want to weep, is there anything I can do to resolve this?