Mistwalking Compass
While mists were always a dangerous territory to get into, there were times in history when it was not so life threatening to go through them. There are many paintings and records and remnants of devices that made that possible. Even though no one can be hundred precent safe in the mists, there used to be times when it was as normal part of a human's life as walking on the streets. Where you also are not hundred percent safe all the time.
Mistwalking Compass seem to be a palm-sized device helping people navigate the treacherous territories of the world, where you can't always see the monsters approaching before their chomp you. It is most definitely a device and not a magical construct, as magic tends to do weird thing in the mist and even the currents seem to be avoiding them fiercely. It seems to be part of the naturally occuring weather patterns of the world. It is a very common occurence that certain magical amulets or weapons stop working the moment you step into the thick of it. (Which is coincidentaly also when you kind of need them the most to work. Don't buy your equipment cheep, kids.)
It consists of several interlinked discs of various metals and little crystals. There is also a dial and coordinates measurements along them. It is presumed that was not only showing the correct directions to its users, but was also able to light up when certain anomalies (such as monsters) were detected, giving enough time to find shelter or a different route. There are many kinds and sizes that have been found in various archaeological digs all around the world, but sadly the technology how to make, repair or create them seems to be completely lost to the ages.