Curse of the forest

Debuff
Curse of the forest is curse that is applied by being in the cursed forest region, the debuff description reads "The forest is cursed, it's easy to get lost in the mist"

Buildup
it builds up at a rate of 1 instance per second and reduces by 4 per second

Effect
Once you reach 100 instances, you will have greatly reduced visibility and both your map and mini-map will be covered with fog rendering them unusable.

Immunity
You can gain immunity by wearing the the Shroud of the forest, which is unlocked by killing The old wanderer.

Workaround
You can still see your map marker which could be an effective way to traverse the mist. You can place the map marker before you enter the mist.