Think the dude meant lunar diplomacy. But since I don't think you'd get the joke either way...

Once you've completed all the challenges, talk to the guide in the centre, and he will ask if you are ready to face the ultimate challenge. Say that you are, and you get to face "Me", a level 79 opponent who's pretty easy and is geared to your stats. You will occasionally be teleported around this arena, but this is more annoying than dangerous. The chats are quite amusing from "Me", so listen out! Once you have defeated "Me", talk to the guide at the centre of the Dream World, then exit via the lectern, and go and talk to the Oneiromancer again.