Roll a d20

This is a common situation where the DM hates a particular player and for no reason asks him/her to roll a D20, in which even on a perfect 20 they die in some odd way, usually not agreeing with the 8th amendment of the United States of America. More ways this is used, or should I say stretched to its limit, is when the player rolls a 20, they usually get some kind of reward, like a pet dragon, who then promptly mauls the player, and kills them. This is just one of many possible things that can happen when the DM says "Roll a D20." One more way this is used is when the DM asks you to roll a save that you cannot win no matter what, and he just wants to see you panic.