Grimfiend

I guess I'll just take the ladder that I seemed to miss every other time. Sorry for the post!

Not sure what I am missing here, I've scoured the entire mine and can't seem to get to Cahil. I've defeated the drake and even found his switch, but no idea how to get past the gates or where to go from here. I have a feeling there is a hidden scripted spot on the floor somewhere, but again, I feel like I've been everywhere. Any help would be appreciated!