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.
As the PCs cross a brigde/tree over a deep river they see the glimmer of gold and jewels lying at the bottom. At further inspection they notice that it is the skeleton of a man still holding on to a sack of treasure. Will the PCs try to dive to get it? What killed the man? Did he simly not let go of the bag he could not swim to the surface with? What cleansed his bones so? Are there flesh-eating beings that dwell in the deep? Can the players resist the chanse of being wealthy for once?