I was working on a prototype for the iPhone game, however, if we have a story already, then there is no point :p
Mist
PS Here was my story.
We are all members of a group called the Game Maker's Garage, which is the only living group of humans (that we know of) left. You (the player) are a newer member of the club, which has been sent out to try to beat back the goblin/other creepy monster hordes to allow us to create forward bases. You start in the garage, and talk to silver, who sends you out to beat lets say 30 "level 1" monsters. once this is done you go back to the house and notice lets say gandolf missing. When youy ask silverwind why, he says that gandolf went ahead to form a forward base, you go to the forward base and basically do the same thing.
At the end you make it to GMG Ghost's Forward base and get his sword of the GMG God. You go out and defeat the leader of the invaders and save the world!