Originally posted by Francesco da Vigiliae:

An important thing to note is that the Mistlands biome will only generate in areas you have not yet discovered. Therefore, if you have explored a lot of your world, you might be better off starting a new one in order to actually be able to travel to the Mistlands.........
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the question is: why did you missed the info given by the devs that the new biomes are generated when you discover them and NOT if you allready have them discovered

why did you notice this right now? scince it was the same a while ago when they finished the plains

they told us allready, so no reason for uprising right now - the game is still under development