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.
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.