I'm doing a fresh install of Windows soon-ish and want to back up my permadeath rogue save file. I found the .sav file in documents/gaslamp blah blah folder but just in case there was some other data required for it to work I removed it as a test and ran the game. I could actually still see my character name there when I started the game but when I tried to load it the game crashed, which was weird. I inserted the file back in there and everything worked perfectly. Is there some other file besides the .sav one that I should back up for the save file will be complete and I'll be able to load it again?
You need loadsave.dat as well. It determines which save files are active. The bitmap_HeroName.sav files are, as far as I know, just the preview images that are shown when loading a save file.
