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.

There is a mod that can force new biome assets to laod into a pre-generated world. So you can add the new Mistlands to a preexisting world.

This mod: https://valheim.thunderstore.io/package/JereKuusela/Upgrade_World/

It should work just fine if its single player. You will need the server requirement stuff if you are tweaking a server world.

Word of caution. If you have a base in the empty Mistlands area, it may end up trapped in the cragrock assets when the new biome forms.