Resurrecting this thread because I am also having this problem while fighting Nemnok.
It always happens 15 - 20 minutes into the fight, and it only happens to my Watcher. It doesn't matter how much health she has or how much Nemnok has. It's happened when he was at 5%, and when he was at 75%. My watcher has died from full with no injuries, and she's died when she's been unconscious with one for three minutes beforehand. Nothing I do seems to make a difference, but about 15 - 20 minutes in my watcher dies and I game over, every time.
I've tried the fight with a Death Wardstone up and that didn't make a difference. The pet I have out every time is Prissy.
