I don't know why there is a veil of secrecy around it. If anything, I think it would be better to keep the community going since this game gets old playing solo.
Dragon, if you've beaten legend mode, that character can now play in a world with higher level drops and higher level monsters. To get there you have to hit "play now". It seems to be very random and your progress is never saved (as far as I know). Sometimes you'll join another groups' game of else you'll be on your own.