Big J Money
Adventurer
This isn't exactly an answer, but if you want to explore the philosophical (or rather, psychological) ramifications of Devil's Sight and Darkvision, consider this:
You are someone who is immune to the dark. You don't know what darkness is because you can't even experience it unless you close your eyes (do these creatures in fact close their eyes; or if they do, does it really take away their vission or can they still see?). Your entire culture doesn't know what darkness is and never has. There are foreign races that speak of this thing called darkness, but you can't comprehend it. It sounds terrifying, but they must be telling tall tales, since it clearly doesn't exist anywhere. It's just their boogeyman. Or perhaps its a weakness that makes them inferior.
Now imagine a magic powerful enough to actually create a darkness that affects these darkness-immune creatures. That could be a truly terrifying villain.
You are someone who is immune to the dark. You don't know what darkness is because you can't even experience it unless you close your eyes (do these creatures in fact close their eyes; or if they do, does it really take away their vission or can they still see?). Your entire culture doesn't know what darkness is and never has. There are foreign races that speak of this thing called darkness, but you can't comprehend it. It sounds terrifying, but they must be telling tall tales, since it clearly doesn't exist anywhere. It's just their boogeyman. Or perhaps its a weakness that makes them inferior.
Now imagine a magic powerful enough to actually create a darkness that affects these darkness-immune creatures. That could be a truly terrifying villain.