Lord Zack's Planescape
Earth is a planet on a Material Plane that is waning in magic (though some believe that situation has begun to reverse). Several pantheons have had presences on this plane in earlier ages, but currently only a few are commonly worshiped. Some have noted some similarities to Oerth, leading some to believe that it is a parallel world. It is more commonly known by other names in some quarters, such as Midgard by the worshipers of the Aesir and Vanir (though that term can be applied to any world the Aesir and Vanir are worshiped on).