It looks like you have run into a bug here... Do you have a save right before you entered the Black Cove (I know, losing a few hours of progress is irksome!)? Try verifying your game local files via Steam client and load the save game before the Black Cove. Hopefully, the bug will be gone then! If it does not help, you should maybe reinstall the game completely (you can keep your save games).
If it really is a bug, then Im probably going to have to restart from scratch.
Cleared out the cove ages ago and since then killed Braccus and did most of Luculla, I was under the assumption that there wasn't any more to the Black Cove until I realised that my heroes were vastly underlevelled in Luculla Forest and decided to backtrack.
