Doesn't really end too well for those that beat him.
He then asks you a question which circles around "do you want to be/get to/receive X?", while X is something you really want. need or don't believe to exist - it's a tricked up question and you're sure that he keeps his promise.
As such you would say yes. That's all he needs.
And then you get what he promised, just not with the results that you linked with it.
It's more of a never-ending stressing task which follows this promise, as such exhausts you out of your newfound possibilities with side effects.
And as he has all time in the universe.. you still lose.
Don't ask me where I got this experience from.. ?