-Doing Adventurer's guild requests/killing mobs
-Clear dungeons and sell your drops from there. Or equip them since they're better than what's offered in the shops.
-Slums upper right corner at night.
Yes, this is very useful! From the looks of things it seems that you were slower than both of the bats, and they inflicted you with poison on their first turn.
The issue seems to be that scripted battles(ones in which enemies are predefined, rather than randomly generated based on the area encounter table) do not process damage over time effects properly, so when you ended the turn by attacking(turns in this game are incremented once everyone on the battlefield acted), instead of reducing your health due to poison damage, it crashed.
This makes it much easier to address the issue, thank you for posting it!
Hmm...when did you download the game? 3 days ago I uploaded a patched version that addressed this and a few other issues.
As for the bounties, the entire adventurer's guild is in an experimental state right now(it will be fully functional in the next update). I didn't expect so many people to continue playing even after unlocking every scene in this version