Mortal souls trapped in mere objects.
As a mortal dies, their soul leaves the body and is soon reaped by a hunter sent from the Underworld, to then be recycled in the circle of life and death for their eventual incarnation.
However, if one is fast enough, they may trap a soul right as it leaves the body (that may include their own, such as what happened with Mallory) into cursed urns and other such objects (or directly to a vessel), which all exert a strong pulling force onto souls in the wild.
These cursed urns are, in reality, exactly the same as the vessels these souls later occupy; both enchanted objects which pull souls toward them until one occupies it. These articles are enchanted through a ritual, where minuscule fractions of the (not always willing) participants' souls are deposited into the item. These rituals are usually performed by various people, to minimize the amount used, especially for larger vessels, as the quantity is proportional to its size.
Then, to imbue another object with a soul after its release, the cursed urn is broken open, and the released soul must be guided towards its new vessel so it has no option but to accept its fate as an artificial. As the Juntan are essentially the embodiement of demise, they are known to invoke a primordial phobia in any witness, naturally the soul tries to avoid it as best they can, and they instinctively immediately rush to whatever form fits them best, usually humanoid or at least animal-like (essentially anything that can naturally move; although in some more uncommon scenarios they can be imbued to any other enchanted object; they will still be able to move, but in extremely limited ways).
Artificials "die" (have their soul released) whenever the vessel is sufficiently damaged, usually at their cores, such as the head and torsos of sculptures of mortals and creatures. They too can feel pain, similarly to how any live body would react, but it does depend on the material they're composed of; those made of very fragile materials such as porcelain are extremely delicated and can be hurt and killed quite easily, while those made of tougher things such as marble and stone are far more durable than common mortals.
the Possessed Sigil, used in rituals of enchanting, and often to brand cursed urns and other bewitched items.