Dream world. You will get Carver once you do a quest for the first castle. Then when you make it to the dream world (well I won't spoil that plot point for you), you will get a third character, and on the tower for the mirror you will get your fourth.
I have played some of it, we got it a week before launch, and got the review online the day after launch. Lots of grinding.
The plot twists in DQ6 make me rethink certain things. Certain games had certain content that I thought they were the first game to present that idea. As I have played this game I realized they were not the first ones so they were not as innovative as I once thought. Again, don't want to spoil it for you.