There are three pieces of advice I give every youngling who wants to become an explorer: pack an extra pair of socks, never eat yellow berries, and just don't bother with the Mistvale.
Set between two mountain ranges in the middle of the Kwal Dominion, the Mistvale is, as the name suggests, perpetually filled with mists, no matter the time of day or year. The mists resist all known forms of scrying and divination, and they are disturbed but not removed by strong winds. Most brave or curious souls who try to enter the mists simply wander around blind for hours, before finding themselves emerging back outside the mists none the wiser. A rare few who enter are never seen again. Whatever secret the mists are hiding, they clearly mean to keep it. The Mistvale has been in its current state as far back as records exist - there is even a mention of it in an ancient Naian text dating back from before the Cataclysm.