A.K.A Squeal of Fortune 2.0.
How to play:
that fucking goblin 1 of 5 treasure chests and get ready to be disappointed.
Small Exp lamp
Needless and unwanted cosmetic items
Shitty weapons and armor
lucky/dragon items (0.0002% chance to obtain)
The chances of picking a rare chest is less than 1% so don't count on ever seeing it. Even if you do pick a rare chest, you will probably get something like a hat. Jagex is soon to be sued by the makers of Team Fortress 2 for copying this clever ruse.
Despite Jagex's repeated insistence that your real-life wealth should not affect your performance in game, you can actually buy keys with real money. This of course is all just Real World Trading.