Cursed City

I defeated the Necromancer, but now the library is inaccessible, and I can't reach the other castle. What should I do?

I have some questions about this. Actually, you can only block access to the second castle if you cross the region (after the Knight), which will prevent you from going back. There are no scripts on the Necromancer that would cause this. If by the "second castle" you mean the Necropolis, you can't reach it due to the storyline (even though the garrison's defense has been weakened), but the second human castle is perfectly accessible.