They say you give up a few things, chasing a dream. In those mists that's the literal truth, for every dream of yours that comes true, a piece of yourself, mind, body, or soul, gets taken by the mist. Worst part is, you won't even know what the cost of your dreams are until you go to leave, and by then you might not even have a mind left to change...
A fragment of the mists of creation, drawn to those desperate to make their dreams come true. Suitable for any magical fantasy setting.
Game Cliche 2.
Upon learning about "the five ancient jewels" or "the nine legendary icons" or whatever, you can be quite confident that Saving the World will require you to go out and find every last one of them.