Necromancer castles (and none of the others) cause my game to crash upon two specific instances:
1: When I try to go into a castle with or without a hero.
2: If I do open the castle screen without crashing, it crashes when I try to select any of the buildings.
This only happens sometimes but it's a regular pain in the neck and it only happens with Necromancer castles for some reason. Necromancer towns (castles without Forts) do the same thing.
I end up with an Exception error message if that means anything.
EDIT: Upon further examination, I've come to realize that a lot of the crashes I had during 8.0 were because of the HD Launcher but since then, they've fixed a lot of the crashes I was getting, so I was able to narrow it down to one specific situation.
I think the Necromancer castle crashes are from the mod itself because it's the only one left that I regularly experience and I've sent numerous bug reports to the HD Launcher team through their automated in-game crash report system (which is pretty cool).
I've installed a few version updates since I was able to pinpoint the Necromancer crashes, and if they haven't been able to fix it, that leads me to believe it's a bug in the mod itself.