sfedi said:Hyp. you're right.
I wonder if that rule applies for the Fog effect, though.
Since the concealment granted is because of the intervening fog between the spotter and the spotted. And that implies that the conecalment works both ways.
Other effects are more explicit about giving concealment if someone is here, there (i.e. Darkness) or affected by the spell (i.e. Blur), but Fog creates an effect that obscures vision, depending on how much intervening fog is between the creatures.