Although it is a gift that is often disregarded - overlooked until some aspect of it is lost or taken away - it is our physicality that that makes us more than observers.
Found predominantly in the sewers, particularly of older cities, and often confused with other common slimes and fungi, a Lichmould is actually a more substantial and far more complex organism. A creeping and shuddering translucent grey jelly - each one a unique organism with a nebulous and undeveloped intelligence - they are carnivorous scavengers and opportunistic carrion-feeders. Draping themselves over the remains of small animals (rodents, for the most part) Lichmoulds envelop the corpses and then, even as they consume the decaying flesh, they crudely articulate whatever is left of the creatures’ skeletons in order to continue their search for sustenance.
Whilst Lichmoulds are able to adjust their own viscosity and elasticity (in order to serve as replacements for the tendons and muscles that are being devoured) with minute and extraordinary precision, this adaptability is traded for the strength and surety of the original tissues. Furthermore, and although their function is undoubtedly remarkable, they also lack the intelligence or the sophistication to reorganise or recreate the anatomical structures of the carrion on which they feed. Instead they use bones as they find them, relying on rudimentary and instinctive understandings of how various types of joints function in order to create shambling approximations of absent animal vitality.
These ambulatory scaffolds are only ever temporary. Once the last scraps of meat have been eaten away, once the last morsels of marrow have been digested entirely, a Lichmould will usually abandon one borrowed form in favour of another. In the absence of a suitably nutritious replacement it will conserve its resources; forced to either detach itself from a host (and utilise the advantages of its more fluid natural state to continue the hunt) or to choose to enter into a sort of suspended animation, clinging to used-up bones and waiting for more prosperous circumstances to present themselves - no matter how long that might take.
Whether the migration is immediate or not, it seems that Lichmoulds either cannot develop or cannot retain any kind of memory as to how their previous host forms were constructed. If, for example, one was to move from a discrete and complete set of remains to a disarticulated or damaged set from the same species, it could not reorder them into a more practical or optimal structure. In such cases - or in instances where pieces of multiple bodies have been mixed or intermingled - a Lichmould will animate them as though they were one animal: A chimera, articulated mechanically efficiently but without a single spark of imagination.
The haphazardly-conjoined skeletal creations that result, whilst inarguably more grotesque and unnerving than their more complete counterparts, are especially feeble and fragile. Unneeded, unnecessary extremities flex and twitch ineffectually, providing more drag than drive, and can slow their shuffle to a virtual crawl. Still, the desire to expand seems to override more basic needs and, when a particularly bounteous corpse-harvest allows a Lichmould to grow large enough, it may consume and encompass additional remains whilst remaining anchored to already exhausted ones. As long as a ready and plentiful supply of decaying flesh is available, Lichmoulds seem loathe to surrender whatever bones they have incorporated into their being.
Theoretically, there is no physical limit to the number or the mass of skeletons a Lichmould could grow to encompass and animate, a grey tide pulling itself forward on an army of borrowed limbs it cannot properly operate. Nonetheless, the largest known example is likely the Ungvár Horseman; a nightmarish pseudo-centaur that was hurriedly torched after it staggered, faltering and flailing, onto the fields of a rural farm. Instead their harsh environment and restricted opportunities to feed - along with human actions spurred by an instinctive revulsion to both the sight and the rank and rotten scent of them - work to curb and check their spread.
They may be viscerally repellent to most who encounter them (whether in their natural state or in possession of a skeletal host), but Lichmoulds do not present any real or meaningful danger and are, in fact, extremely vulnerable to various forms of harm and damage. Skinless, their gelatinous bodies are porous and semi-liquid - tissues undifferentiated until certain, specific needs arise - leaving them susceptible to chemical disruption by anything sufficiently acidic or alkaline. Additionally, they can be dried out by desiccants (or by the warmth of strong sunlight) and even otherwise-immiscible accelerants will cling to a Lichmould, making fire a dramatic but cruelly effective method of destroying them.
In some ways, Lichmoulds are at even greater risk when they are animating remains; when their presence - and, by extension, their work - becomes more apparent. They lose the anonymity of the inert and express the immediacy and urgency of their existence as a form of life. Previously disregarded, they become a stark representation of mortality, of life built on the back of death and decay, and whilst their borrowed bones might lend them some semblance of structure, they become more vulnerable to physical force. With the anchoring to individual bones being stronger than internal cohesion, a concussive blow can scatter the skeleton and tear the Lichmould apart in the process.
Although they can easily, and understandably, evoke a sense of horror and dread - and there can be little doubt that their existence has lent to the creation of much of the myth and legend around the undead, of reanimated corpses and shambling skeletons - there is actually more than a little of the tragic (perhaps even the pathetic) in the habits and behaviour of the Lichmould. With little apparent advantage to be had by the taking of a host, their drive to appropriate a more solid form seems to speak to a longing rather than a need; a desire for an effective and tangible physical presence.
Given a complexity of intent and motivation that seems at odds with the relative simplicity of the Lichmould as an organism - specifically the paradox of being able to act against their own best interests in order to obtain and retain skeletal hosts - there is a perhaps undue amount of speculation around their origins. Though some argue that we are merely anthropomorphising actions that are governed by a more complicated set of input and stimuli than we yet understand, others have worked to demonstrate links between Lichmoulds and fringe folklore about curses that devolve or disembody: Casting them as sentient life forced into a weak and ephemeral form.