So I know this is a little late, but I recently started playing through this and I found it is impossible to recruit Cormag in Eirika's Route Chapter 13. Cormag is Replaced by Ephraim, and Ephraim is not a flying unit, because of this he cannot move from the space he comes in, which is a mountain. I even tried cheating and making Lyon(Eirika Replacement) into a Wyvern Knight so he could talk to Ephraim, but for whatever reason, the talk button did not appear. Any on run into this issue, any tips?