Fun and twisted. Combined with a pc that has the curiosity flaw (or better yet a player with it) you have every excuse to send the pc running across the world in search of know-it-all sages, magic keys, and anything else they think may open it. (Of course once they *do* manage to get a deity to open it or find out there's nothing inside they may well try and fit the gm in any conveniently nearby box, depending on their sense of humor.)
Oh and Pieh, do me a little favor and put your idea up as a sub linking back to this one so I can give it a proper vote and comment (+1 is too little for the idea). It's good enough it it's own right to stand alone.
Edit: One little question, Why isn't this a golden submission yet? It certainly deserves to be one. Go to Comment
I like that orb by itself, and it seems to fit in with the other orbs that Moonhunter has presented.
Good submission, although we might consider saying "please" to the author before submitting derivitive works. As long as no one has any problem with what we're doing, I don't see how it's an issue. :) Go to Comment
A new substance is found in an out of the way area and kept very quiet. It is found to make a perfect counterfeit diamond. Only the most expert of expert appraisers would even have a hope of noticing that it is fake. Only one problem: if it gets wet it starts to slime and if it is saturated, it turns into a glob of gel.