This is a glass jar with a silvered rim and legs for support- it can stand freely on its own or be carried with a strap. The jar appears to be filled with a thick, opaque mist that sluggishly rolls and boils over itself as it moves, it gives off a dim green-blue glow in darkness.
The lid of the jar is made of a pure silver and is fastened with the glass in such a manner that it cannot be opened; only a tiny twisting part in the center can be turned to open the jar. This pinprick of an opening lets out a tiny bit of the magic mist over time- much like a censor or incense burner. Usually you would open the jar and either leave it in place or carry it with you; either way after one turn of being open the air is filled with a thick mist. This fog seems to take over the local reality- birds go silent and the sun is dimmed. If you are indoors the fog seems to rise from the floor, if you are outdoors it whisks around nearby trees as though hiding out of sight.
Once the Jar has been opened for one turn and the air is filled with mist- replace all wandering monster encounters with Hu'Tuli Figments and Hu'Tuli Entities. These encounters take the place of normal ones- these only apply to wandering monsters, as the magical fog keeps away other foes or makes them lost when trying to find you, thus you only run into the figments or entities instead. However stationary encounters- such as stumbling across an orc's camp, will still trigger as normal. If other people are within the fog you bring for at least a turn, then they too are subject to this rule.
After the jar has been closed, it takes 1d6 turns for the fog to dissipate while indoors or 1d2 while outdoors. When the fog is gone, the world will return to as it was.
Whenever you roll for wandering encounters; there is a 1 in 8 chance you will encounter the Hu'Tuli Entities, otherwise, encounter Hu'Tuli Figments. As the Hu'Tuli Entities are much more dangerous; their coming is foreshadowed by a howling wind. If the players stuff up the jar immediately and run or hide; the entities will disappear 4 rounds after combat is initiated, as though the mist just dissipated enough to no longer support those otherworldly foes.
Hu'Tuli Figments (1+2 HD, +1 To Hit, +2 AC, Fog Baton attack at 1d6+1 [cold damage], ghostly apparitions, made of mist)
The Hu'Tuli Figments appear like shadows. They look like people you know, barely obscured by the fog. Getting closer doesn't show more detail, that's just how they look. They attack with batons made of the mist- which pass through physical matter. When a baton hits your body, it goes right through, but it chills you to the bone dealing cold damage. As this damage is not a physical tearing of the body, it can be cured by simply warming up at a fire, but enough at once can be enough to kill.
The beings are ghostly and as such cannot be hit by normal weapons- they pass through them. Only magic weapons, weapons made of silver, spells, or special kung-fu attacks can hurt them.
The Figments are also made of mist, meaning they can move through any kind of terrain and disappear and reappear at will- meaning they attack from all sides and cannot be surprised. Certain spells or techniques, such as blowing on them with a magic fan, can break them apart and stun them for 1d4 rounds. While they appear like ghosts, they are not undead and cannot be turned.
Hu'Tuli Entities (4 HD, +2 to hit, +4 AC, Windchill attack at 1d8+2 [cold damage], Scythe attack at 1d6+2, ghostly, howling, windborn)
The Hu'Tuli Entities look like rough humanoid shapes made of a smooth, gray ice with holes. The holes in their body is also how they create the wind sound- the howling wind that accompanies their arrival is their trademark. These Entities are much more powerful then the Figments, and seem to possess a greater intelligence. Where as the Figments seem to just be following their nature or attacking anything they sense as prey, the Entities almost seem to be intentionally targeting intruders into their realm, as anyone using the Jar has one foot in a different plane.
The Entities blast out elemental cold in the form of a wind blast that hits anything in front of them, every round. Treat this like a ranged arrow attack. They also attack with small metal scythes they hold in their unformed hands; spare scythes can be seen hanging from the holes in their body, the hooks flying off when they are struck by a hard blow.
These are magical creatures; solid but still as spirits. They are somewhat transparent but are certainly more physical then the Figments. They are still immune to normal weapons and require magic attacks to be defeated. Additionally, their signature howl is their most frightening feature. Untrained hirelings and animals must make a morale check or flee when they hear the sound- anyone who flees will be lost to the mist, and must make a saving throw or be trapped in that cold, misty realm if the Jar is closed again before they are found.
Finally, as Windborn creations they are immune to the normal tricks that work on the Figments; they cannot be pushed away or harmed back by winds. This ability also extends to supernatural winds, as well as making them immune to being knocked back, shoved, or knocked prone- as their body will float back up, carried by the stringing mist.