The Final Mourning
The Mist appears to have a subtle and varying smothering effect on the life force of plants and creatures. Plant life becomes dormant, entering a permanent winter-like state. All trees including evergreens lose their foliage and appear to be dead, and grasses wither and blow away. Animal life can no longer sustain itself without plants to feed on and has to migrate elsewhere or perish.
Creatures traveling in the Mist can rest and heal as normal; the major limiting factor to survival is that there’s no foraging or hunting to be had. Food and water created by magic come out obviously spoiled and foul, and purification spells don’t work at all. If a living creature dies in the Mist, its body doesn’t appear to decay for as long as it remains within. However, it’s known that dead animals and preserved food supplies become poisonous to eat if they’ve been in the Mist for too long.
The Mist seems to give rise to dangerous and unnatural creatures and phenomena that can end an expedition before explorers have a chance to run out of supplies. It’s unknown how these creatures survive in the Mist; perhaps it can sustain the things that it creates.
Since the Final Mourning, the Mist is spread across the entire continent of Khorvaire. There are areas where it’s as even and constant as it was after the first Mourning, but there are also areas where it dwells and drifts away, as well as areas that stay relatively clear. The city of New Sharn and its colonies exist because they’ve found a way to create a magical exclusion zone that keeps a large area free of the Mist.
Once the Mists manifest in an area, the plant life dies off over a period of a few weeks. If the Mists drift clear for long enough, the local flora returns to life in the same period, and usually makes a full recovery in about a year. Also, the bodies of any dead creatures begin to decay as normal.