I fight Grimgor manually and win.
The first dump is after it showed the post-battle loading screen and then CTD.
The second it didn't show the post-battle loading screen, just went black for a bit then CTD. In this instance Orion died while everyone lived in the previous dump.
Declare war on Grimgor & invite allies
Win battle manually
Details of any solutions that have already been attempted:
In December I ended the turn instead of battling and the game kept on rolling until I fought the same lord again (Greenskins again) and then crashed post-battle.
I stopped playing in December because I couldn't get a game that didn't crash at some point. All crashes have been from post-battle against Greenskins. I will wait and see if you guys can fix it.
I'm going to try reinstalling the game now and will report back if it fixes the problem.