HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

Yes, the map is called "Sword Saga," here it is. Yesterday, late in the evening, I continued playing on the same map, and the game crashed again on 1-2-6. :( I'm attaching this save file in case anyone wants to investigate. I'll try starting over and see if it only happens in my playthrough. I suspect that this might be related to the map author making changes using a non-standard editor, but rather with some special utilities (a patched editor, an editor for some mod...). This is supported by the following observation: a number of heroes have custom names and biographies, but the checkbox is not checked, as if they were standard heroes; however, if you click the checkbox, the biography is deleted.