Extant members of the family Ossidae fall under one of three genera:

• Necros, which houses the family's common ancestor and single "pure" descendant, the sexually dimorphic N. lictorum
  
• Os, which houses a wide variety of species descended from O. gigans and collectively referred to as skeletons
  
• Oscuro, which houses a regionally-isolated species also descended from O. gigans

Skeletons are highly intelligent and robust creatures that are among the most widespread of all non-migratory species. Due to their astounding hardiness, members of this genus have been discovered in nearly every imaginable climate and ecological niche - from the more urban regions surrounding Lothric kingdom, to the wilder regions surrounding the far north Drangleic kingdom. They are even suspected to have thrived in the extreme conditions common in the past, before widespread human and lordly development; much like the coelacanth and shark, skeletons have persisted mostly unchanged for ages.

Despite their lack of visible musculature, skeletons as a whole are both remarkably strong and agile. The common skeleton can lift 1300% its body mass, and is capable of quick leaps and dives. Skeleton eyes are often dimly illuminated via necroluminescence, which allow them to easily see through most disguises, and also give them excellent vision in low (or no) light. Generally lactivorous, skeletons assume a bipedal posture on plantigrade legs that allows for tool use in their forelimbs, and are known for their calcified outer shells that render them impervious to most harm.

Skeletons are social creatures, often travelling in groups of four to ten. Like crows and Germans, a large group of skeletons is referred to as a murder. Skeletons have complex social structures and hierarchies, and higher-ranking members of a group will often adorn themselves with garments or jewelry. Most high-ranked skeletons display a preference for gold and brass decorations, while intermediate ranks make do with fabrics and iron, and the lowest go completely bare.

Despite the wide variety of ecological niches skeletons inhabit, many display a slight preference for darker, cooler areas. As such, large groups of various skeleton species will often co-ordinate to excavate massive dens, known as catacombs, which then house multiple neigbouring skeleton groups. Many of their physiological adaptations seem optimised for this environment as well, suggesting that their common ancestor may have lived in such an area.

While neighbouring skeleton species will co-exist peacefully, skeletons are highly territorial towards anything outside of the Ossidae family, and will swarm intruders with great prejudice and regenerating numbers until they flee or are killed.

Skeletons primarily communicate with one another through vocalisations known as puns, though dialects specific to a certain species or region are common. They may also employ gestures and a distinct behaviour known as rattling, adding an additional layer of complexity to their communications that make accurate translation difficult.

The ability to communicate with members outside of their own species is unique, and allows for greater coordination of their social structure, which often includes multiple skeleton species.

Scarce few skeletons have been seen to possess knowledge of metallurgy, though with the commonness of Falchions, Scimitars, and trumpets among the various species one can conclude that a particularly resourceful skeleton able to find a suitable heat source may work metal.

The following sections will detail traits unique to specific species within the Ossidae family.

• Necros primarchus (Gravelord Nito)
  
• Os gigans (Great Skeleton)
  
• Os familiaris (Common Skeleton)
  
• Os rota (Bonewheel Skeleton)
  
• Oscuro ossum (Darkwraith)
  
• Os trinceps (Skeleton Lords)
  
• Necros lictorum (Finito)
  
• Os carthensis (Carthus Skeleton)
  
• Os rex (High Lord Wolnir)
  
• Brachyura Pseudosseus (((Hat Skeleton)))

The oldest recorded member of the Ossidae family, no primary observational information is available on N. primarchus; the little recorded information regarding this proto-skeleton that does exist is not very fleshed out.

What is known of N. primarchus is that it was a mostly sedentary species, very rarely venturing from its den. Much like its descendants, N. primarchus was quite durable and possessed great strength. However, its size and maximum lift far surpassed that of the extinct O. gigans.

Unique to this species was the ability to simply spawn "lesser" versions of itself - by shaking off loose bits of bone from its body mass, N. primarchus could "create skeletons" through a rapid form of budding. This process may have been origin of O. gigans, and thus the rest of the modern skeletons.

Based on stories passed down by Drakeblood K***hts and the Archdrake Sect of Lindelt, N. primarchus may have also possessed the ability to disperse a highly virulent toxin over a wide range. The Archdrake Priests in particular insist that the toxin was potent enough to kill dragons - which were immortal.

The oldest member of the genus Os, O. gigans' relationship to modern skeletons is comparable to that of dinosaurs and alligators. Suspected to have appeared early in the First Age of Fire as a mutated budding of N. primarchus, the "Great Skeleton" was quite different from its predecessor, but possessed many traits that would be preserved in its descendants.

Instead of N. primarchus' complex body and digitigrade legs, O. gigans possessed a relatively simple body and plantigrade legs which gave it a more upright posture. Despite being relatively cumbersome, O. gigans marked the beginning of the trend for skeletons to become more lithe and compact; physiological traits like its thiсk bones and height of four metres are both noticeably reduced in its contemporary descendants.

Despite its "brutish" appearance, O. gigans was still quite intelligent - demonstrating both dextrous tool use and ballistic spatial awareness in low-light environments.

Secondary information suggests that there may have been a "feral" subspecies of O. gigans that coexisted in their habitat. However, ███████████████████████████████████████ ███████████████████. If any extant descendants of this subspecies are discovered, it is strongly advised ████████████████████████████████████████. Do not ████████████████. And above all, never ████████████████████████████. [REDACTED].

With their strength, agility, intelligence, and near-extremophile resilience, members of Os familiaris can be found literally anywhere - from the heights of Archdragon Peak to the depths of the Abyss, and everywhere in between.

The most widespread and well-known member of the skeleton family, O. familiaris have become a cultural icon among humans, their likenesses often used to adorn flags, garments, pottery, and other miscellaneous items. Even the famous proverb "Noli Soccombere, Os!" (lit. "don't give up, skeleton!") refers specifically to O. familiaris and its infamous tenacity.

Some members of O. familiaris appear to have a keen awareness of their resilience, behaving in an almost reckless manner. In the rare case that they are harmed, they will often collapse and "feign death", luring the intruder into a false sense of security before "reassembling" and resuming their attack. If repeated attacks fail, they will simply collapse and wait until the threat has left the area before rising.

One of the most recently differentiated species, O. rota is a very close relative of O. familiaris. The distinction between the two is quite readily apparent though - O. rota possesses a spiny outer growth, an adaptation meant to discourage predation by the intrusive species H. autisticus (Thorolund cleric).

There has been much debate on whether O. rota should remain a distinct species, or be reclassified as a subspecies of O. familiaris. However, aside from its obvious physical differences, O. rota also displays significant behavioural differences from O. familiaris that parallel the differences between the chimpanzee and bonobo; Bonewheel skeletons are markedly more aggressive and territorial than their common cousins, and form larger murders on average, usually consisting of at least ten individuals.

Much like the four-toed hedgehog, O. rota's spiny growth allows it to roll at moderate speed, providing a means of transportation as well as offense - the hardened spines easily tear through soft materials, such as humans. With their greater numbers and coordination, a murder of Bonewheel skeletons is a significant threat; as such it is strongly advised to only observe these species at a great distance.

Due to a cataclysmic flooding event, a small population of O. gigans were isolated from the evolutionary forces responsible for the adaptations seen in skeletons elsewhere. Rather than merely perishing, though, the skeletons gradually adapted and began to thrive in this harsh new environment.

Much like how Australia's geographical isolation resulted in unusual (and often venomous) adaptations, the Darkwraith is significantly more dangerous than their mainland relatives. As it is very difficult to drink milk underwater, the transitional O. gigans became carnivorous out of necessity. This dietary need, combined with the high pressure of their home, resulted in the appearance of O. ossum - an amphibious species that possesses unique traits ideal for hunting in an aquatic environment.

With a compact body to reduce water resistance, but the sturdy limbs of their predecessor preserving their strength, O. ossum is a powerful hunter both in water and on land. Like many apex predators, Darkwraiths may coexist in an large environment, and even co-ordinate on larger hunts, but will generally claim specific areas as personal hunting grounds. As a result, they appear more solitary and asocial than other skeletons.

O. ossum's most unique adaptation by far is their "Lifedrain" ability (colloquially referred to as "the ѕuсc"). Like jellyfish, Darkwraiths possess an arm covered in harpoon-like nematocysts, capable of delivering a potent - but fleeting - paralytic venom. Upon successful envenomation, O. ossum will immediately leap in to feed on the calcium-rich body fluids of their still-living, paralysed prey. The species' intelligence becomes apparent here: rather than ѕuсcing their victim dry, they will often allow the prey to escape so that it may be captured again at a later time.

Early O. gigans that managed to arrive in the northern continent of Olaphis (later referred to as Drangleic) were met with a more peaceful, undeveloped environment than that of their companions in the south. As a result, the skeletons of the region did not form catacombs, but flourished on the surface and spread across the land. Skeletons can be found in nearly every corner of Drangleic, and nearly all are subordinate to O. trinceps.

The most aesthetically-minded member of the skeleton family, O. trinceps' nomenclature refer to both its number of horns and consistent rank in their local social structure. Physiologically, they represent an intermediate phase between the tall, bulky O. gigans and petite, svelte O. familiaris. Their behaviour is also significantly more complex than other members of their family, as demonstrated by a wider variety of preferred tools and tiered social structure.

O. trinceps' most unique trait is its ability to generate bursts of flame by storing shed bone dust in hollow pressurised chambers on their forearms. Upon ejection, the rapid change in pressure heats the bone dust to its flash point, creating dazzling and potent displays of fire. It is suspected that this trait inspired humans to use bone fragments and powders as fuel for bonfires.

Under the organisation of O. trinceps, skeletons of the region appear to have become more civilised and prosperous than those encountered elsewhere - the majority are remarkably non-hostile, but rather content to merely rest and listen carefully to the sounds around them.

Collectively known as Finito, N. lictorum is an unusual member of the family Ossidae; despite being a direct descendant of N. primarchus, they display almost none of the traits common to other skeletons.

Their physical appearance is the most obvious difference - rather than the hybrid endoskeleton/exoskeleton common to its cousins, N. lictorum possesses an endoskeleton surrounded by fleshy tissue - resulting in an appearance similar to H. sapiens. It is unknown why such an adaptation was necessary considering skeletons' inherent hardiness, but N. lictorum does uniquely share its habitat with humans, hinting at potential mimickry.

A sexually dimorphic species, male members of N. lictorum are called Fenito, while females are called Milfanito. Like most species in the animal kingdom, the female is larger than the male at maturity, reaching a height of approximately 3 metres while males settle at around 2 metres.

The species' behaviour is also noteworthy. Fenito act much like their other skeleton relatives, displaying both astounding strength and a preference for catacomb-like environments. Usually docile, its territorial nature becomes apparent when it is exposed to light - it is suspected that Fenito possess stronger night vision than most other skeletons; this hypersensitivity to light will cause the Fenito to experience pain upon exposure, and thus provoke a defensive response.

Milfanito, on the other hand, prefer to live in more open, dimly-lit areas than the males. Much like Aves, they are most well known for their "song" - a method of both long-range communication and mating signalling. The song of the Milfanito is perceived to be calming by multiple species, suggesting the use of infrasonic psychoacoustics.

Due to fierce competition with the massive L. tyrannicus (com.: Great Sandworm), O. gigans that arrived in the desert region of Carthus did not become smaller as they adapted to their environment, like many of their relatives elsewhere, but rather retained much of their size.

At least two subspecies of O. carthensis have been discovered and recorded:

• The "Carthus Swordsman" subspecies bears the greatest resemblance to their Great skeleton ancestor out of all modern skeletons. Lightly armoured with heavy blades and compound bows, these were likely the ones to directly engage L. tyrannicus in the past.
  
• The "Carthus Warden" subspecies is remarkably agile and evasive for its size, its movements often described as "gliding across the ground" by those who have witnessed them. With an almost playful demeanor, they seem to enjoy showing off their acrobatic leaps and flips.

There have been scarce reports of a third subspecies, unofficially called the "Carthus Rogue" by those who have encountered it. Despite being half the size of its companions, it apparently displays traits of both the officially recognised subspecies while also being significantly more aggressive and territorial; it may be a hybrid of the two.

The species' intelligence is demonstrated through feats of complex mechanical engineering, most notably the massive automatic crossbows which allowed them to drive their rival L. tyrannicus to near-extinction. The elaborate, intricate engravings found on most of their tools also suggest artistic inclinations associated with higher thought processes.

An unusual and elusive species discovered recently, O. rex possesses many traits that set it apart from the local O. carthensis and have piqued great interest among osteologists and necrologists.

Another member of the skeleton family whose taxological placement is under debate, O. rex appears to have traits of both the Necros and Os genera, making its relationship to other skeletons unclear. Its elusive nature compounds the difficulty in resolving the matter.

• Its large size and use of toxic vapours are reminiscent of the myths surrounding N. primarchus.
  
• The elaborate nature of its personal adornments are in line with the style seen among O. carthensis.
  
• Artifacts recovered from its den suggest that O. rex is not native to Lothric, but rather migrated from the Drangleic region. This may make it a relative of O. trinceps.

A member of the subphylum Crustacea, B. pseudosseus appears to be a subspecies of the Greater Farron Crab which experienced a geographical displacement 3000 years ago, resulting in their integration with a local skeleton catacomb. In a rapid display of either homoplasy or Batesian mimickry, B. pseudosseus quickly developed physical adaptations that made them outwardly similar to O. familiaris upon maturation.

Despite this superficial similarity, B. pseudossus possesses many quirks in both their physiology and behaviour that serve to easily differentiate them upon closer observation. The most obvious difference is their "hat" or crest, which is actually a mass of vascularised tissue that serves as a reproductive organ. Their "false arms" are derived from a single pair of legs (other pairs forming the "ribs") and thus incapable of actual grasping - Hat Skeletons do not carry the tools common among true skeletons.

Behaviourally, members of B. pseudossus are both solitary and timid, which serve to reinforce their unlikeness from their neighbours. Much like deer, they will immediately panic and flee upon approach, completely disregarding any other potential hazards that may bring them greater harm.

B. pseudosseus is a fastidious scavenger, collecting bits of bone and rock to reinforce their fragile eggs. Upon hatching, the young Hat Skeleton appears very much like a small Farron Crab - the mother will then hide the young away until maturation, when it begins to better resemble a true skeleton. This set of habits combined with their reclusive nature have inspired some to refer to them as "janitors of the catacombs".

Many thanks to the following contributors:

• Gravelord Nito: Praise be upon him.
  
• Skeleton: Body double.
  
• Skeleton™ Kye: Editor.
  
• Hat Skeleton!: Cute intern who will do anything for a recommendation letter.

Questions, comments, corrections, or concerns can be addressed to Skeleton, Head of the Necrology department at the Carthus Institute of Osteology. You likely won't receive a responce as I don't really care, but my publisher says that the above line is required due to some bullѕhіt policy.