The legendary "Owner's Manual", a tome of knowledge describing the creation of the universe, how reality was formed, how to manipulate it, and when the warranty runs out.
Alternatively, have it be like the suitcase form pulp fiction - even after achieving the task they still don't get to find out what's inside it. Have Torm and/or Bahamut appear and take the case, saying that its too dangerous for human hands, but thank the party with a Wish each. Then you can have fun with wishes.
(See that other thread where the rogue got jobbed by his DM)