A visitor to the Northern Katans is likely to come across stories of a strange beast called the wolpertinger, perhaps even a supposed taxidermied specimen. It takes no deep knowledge in the natural sciences to tell the creature is simply a rabbit or some rodent with added antlers, fangs, often bird wings and legs, sometimes even a duck beak. But as tempting as it would be to reject the entire creature as a pure fabrication, somewhere deep under the fabulations and exaggerations there lies a core of truth, a real animal that once lived in South Ordosia.
While much of the ancient Velannic science rotted away neglected during and after the Great Drought, art became the unexpected preserver of natural knowlege otherwise forgotten and lost. The seals and flags depicting the emblems and symbols of cities, army units and even families evolved into the art of heraldry during the Age of Walls, containing much otherwise forgotten information about plants and animals. Eventually the imagery of Ordonic heraldry became divorced from the original subjects, even to the point of being wholly unrecognizable, but the oldest depictions were close to naturalistic realism.
A certain heraldic beast, mostly used by Velanneans, has clear similarities with the wolpertinger: the calopus. Though its depictions are varied, the beast is nearly always a small furry animal with either curving or forked horns, tusks or fangs and legs that may bear clawed paws or cloven hooves. Most prominently it features in the emblem of the Katan Guard, a unit that has protected the ruler of Thelquam since the Dragon Wars. This is most fortunate, because it has allowed for an unbroken line of depictions to be preserved in the oldest still standing city in Ordosia.
The "Loepav Kalopus", or leaping calopus of the Katan Guard was carved in the stone of the northern gate during the rebuilding of Thelquam after the Third Dragon War, and it survived all the tribulations that tested the city since, making it the oldest surviving version of the emblem. In it the calopus appears as a very real seeming animal with a head somewhat resembling that of a hare with fairly long ears, slender legs terminating in just barely recognisable hooves, and a fairly short hairy tail. It also has long curved fangs sticking out of its mouth and short slightly curved horns projecting from above it's eyes.
It is quite apparent that the ancient Velanneans considered the calopus a living animal. Their songs and poetry even preserved details about its diet, such as these verses from the Lament of Ilera: "You are a calopus/ A hare with fangs and horns/ With appetite for leaves and flesh/ Your place is nowhere." The phrase "leap like a calopus" occurs often in ancient Velanneic prose and poetry, usually referring to a particularly impressive feat, but sometimes also more literally describing the act of jumping a great distance.
However the most important surviving reference to the the calopus is a passing mention in the Annals of Greater Thelquam IX, in a passage detailing the famine in the city of Thaquainen in the Southern Katans: "Then the people hunted the calopus, until there were none to be found, nor were there hare nor squirrel nor more miserable game that could be eaten." This one sentence not only reveals that the calopus was hunted for its meat but also hints at an explanation for its disappearance. The Great Drought caused widespread famine and many Velannean animals were hunted to extinction during this time. It also spelled doom for the temperate rainforest of the Southern Katans, the most likely habitat of the calopus.
The story of the "horned rabbit" does not end at the Great Drought, however. Thousands of years later Raqush Il-Khawah's Wonders of Creation describes a very familiar-sounding animal called mi'raj that lives in the Hairas, a mountain range separating Arbaysia from the rest of Ardasia. The mi'raj is a seemingly harmless rabbit with golden fur that has a single black horn projecting from its forehead. It also has fangs that betray it's true nature: the mi'raj is a carnivorous predator that will even attack humans, leaping up to stab them to death with its horn.
While Raqush Il-Khawah was still working on his treatise, Thelmar finished his own bestiary in Thelquam, completely unaware of the Debarian scholar's work. The Thelquam bestiary included the calopus, and Thelmar described the beast in detail, possibly drawing from sources that have since become lost: "It resembles in form the hare, but with the snout of a deer, horns of a talopus and fangs that are very long and frightful, for despite its small stature the calopus is without fear and full of fierceness; a predator in the shape of prey."
The similarities are obvious and tantalising. Thelmar was the first known Velannean author in ages to treat the calopus like a contemporary animal, during an era when it was almost certainly extinct. The mention of the mysterious talopus suggests he was not inspired by purely ancient sources, either. Thelmar provides no description of that animal, but it is mentioned again while he lists beasts that have cloven hooves but do not chew the cud, along with the calopus. The exact wording is "the talopus of Arbaysia", even though other Velanneic sources know nothing of such an animal.
Fortunately Thelmar's collection of preserved animal specimens survived the Great Fire of Thelquam almost unscathed in the temple archives, because among them was one labeled "talopus". Less fortunate is that the collection was since then neglected for millennia, so by the time it came to the attention of naturalists, most specimens, including the talopus, had been reduced to little more than skeletons. Even so, the bones clarified the nature of the talopus and it fit the description of the calopus, igniting hopes that the animal was still alive in Arbaysia. Wonders of Creation was still unknown in Ordosia, so finding it in the "land that hates everyone" without a clear clue was not going to be easy.
The elusive talopus was eventually found in southern Arbaysia on the forested slopes of the Haira mountain range, where the locals knew it as jakmur. It was about the size of a large hare, though not exactly shaped like one. Its hind legs were longer and much stronger than the forelegs, but only two of the four toes touched the ground and terminated in small hooves, as was the case with the forefeet as well. The tail was longer than that of a lagomorph, while the ears, as elongate they were, weren't quite harelike in proportion, especially when compared to the fairly large head. The black wet muzzle was rather deerlike, but out of the mouth grew a pair of distressingly long and sharp fangs. It had been obvious from the skull of Thelmar's talopus that it had had large canines of some sort, but they had been lost, perhaps even intentionally removed, at some point.
Of course the animal also had horns, at least in the male specimens, two black projections about the length of a man's thumb, starting above the eyes and curving slightly backwards. Though there was a pair of horns instead of a singular one, the golden yellow fur that turned dark brown on the mindline and the rump was close enough to verify this was Il-Khawah's mi'raj. And to lend credence to the stories about it's predatory nature, the first animals captured alive were happy to feed on meat, even reportedly killing mice and rats that wandered into their cages during the voyage to Velannea.
Once they reached Thelquam talopuses once again disappeared from written record; for nationalistic reasons the animals were classified as the same species as the calopus of old. They were certainly close enough to the animal depicted in the northern gate of the city - by now known as the Calopus Gate by the common people - and the small beast that had grown into a symbol of Velannic tenacity was exactly what Thelquam needed at that time.
The Arbaysian calopus, or jakmur, proved to be less than its fearsome reputation. They ate more leaves than meat, and preferred bread and fruit to either. When they felt threatened they made impressive leaps as the old sayings suggested, even managing to jump over zoo caretakers that tried to apprehend them. It seemed that the Arbaysian tales of the animals charging their harassers when cornered had more to do with hunters trying to cover up their own cowardice than the fierce nature of their diminutive prey.
Once the study of living and dead calopuses proved them to be omnivores of herbivorous leanings, the notion of the predatory calopus, probably based on their fearsome tusks and tendency to scavenge, was laid to rest. The omnivorous traits and primitive cloven hooves suggested to zoologists that calopuses might be an intermediate between pigs and horned ruminants. They had three-chambered stomachs and didn't chew the cud, so it seemed plausible. However it was later found that they were much closer to leucrotes and hippopotami, in fact they were the closest living relatives of hippos despite the external dissimilarity.
However, all of this doesn't quite fully explains how the legend of the wolpertinger came to be. As explained earlier, the calopus was utilized in Ordosian heraldry, especially by Velanneans, long after its true appearance had been forgotten. With time even its name started to become distorted. In Fritland it became the jacalope or jackalope, in Middle Ordosia the chatalupe. Perhaps the common way of depicting it as a fanged rabbit with small antlers made it too tempting to use in tall tale, or a sighting of a rabbit with antler-like ceratinous tumors caused by a papilloma virus was the initial trigger. In either case people started reporting more or less serious sightings of the creature especially in the Northern Catans, and the common folk came up with their own name for the creature that everyone seemed to know despite never seeing one thesmelves.