Actually, there is a lot of mythology centered around strange events occurring in supernatural fog... I think it fits.
It fits the
theme since we already have fog shield, and fog is essentially superfine mist.
Here's an interesting news clip involving "Killer Fog" that happend in the 50's in london. This actually did happen, its not a myth. Its one of the major events that lead to many of the pollution control laws we have today:
http://www.npr.org/templates/story/story.php?storyId=873954Also, anyone remember the movie: "The Fog" ... although that was the work of things that lurked within
Here I think the card is hinting at things disappearing and then vanishing along with it when the fog dissipates.
Its a cool concept.
I like it myself.
One thing I think would make it more interesting is if it acted on the field slot rather than the creature, and perhaps had a limited duration. Then, any creature that got put in the same field slot would be affected as well. This would fit the environmental like effect, making it more like a real fog or mist