Originally posted by BearRiverBandit:

Do I need to start a new world for the mistlands or can I use my existing world? I still have a lot of my map unexplored so just wondering if I need to start anew or will I be able to discover mistlands in my existing world.

you can do either or, a new seed however will make the mistlands generate better tho.

But remember, only mistlands you have not been at, will have content.