Completed Chapter 14, and then 15 after a couple of attempts. Knowing that reinforcements were going to come from the north-west after so many turns (which essentially led to me losing a character the first time) really helped. With that out of the way, it was on to Chapter 16, in Caelin Castle. There were two characters there, Raven and Lucius, both of whom I couldn’t get to come over to my side (Raven was a baddie and died really early on, and Lucius wouldn’t talk to any of my characters).
As a result, I think I’ll replay the level again, even though I won it with relative ease.