[quote=@Genni]
I'd expect those places would also have an eerie, empty atmosphere which would also have the characters uncomfortably on edge?
[/quote]

Yup. These areas would mostly be deprived of life. No trees no grass, no birds. Eerie and filled with death.

[quote=@Jerkchicken]
So anti-magic zones?
[/quote]

Not necessarily. One would still be able to cast magic spells however it would take a longer charge time and it will be slightly weakened. But fear not. If magic caused the anti-magic zone then magic can fix it.