Gaudecker's ape

Named after the guard officer Eberhard von Gaudecker, who dissected and described the creature during emperor Willibald's campaign in the Snowy Rock Mountains in 1207.
Captain von Gaudecker's company, according to his notes, was accosted by at least three such predators, allegedly working together, and his men shot one dead. Von Gaudecker, being of scholarly disposition, recorded his observation.
The creature is simian in appearance, sporting thick white fur over the entirety of its body, and walking on all fours. Its extremities are well-suited for traversing the rugged mountainous terrain, and one can suppose that the creature could potentially perform relatively intricate manipulations with them. Its teeth structure betrays a primarily carnivorous nature.
The digestive system isn't notable in any way. Reproduction, as von Gaudecker was able to infer from the observable sex characteristics of the studied specimen, is of sexual type.
The most interesting part of the captain's notes, however, is his study of the creature's skeletal structure. He found an especially thick and strong part of its ribcage, practically a continuous bony plate, and examined the corresponding internal organs. He has found that the creature possesses an organ that hadn't been observed in any organism before, and could not explain its purpose. He brought the said organ back to the Empire in a jar of alcohol and took care to provide very well-drawn sketches of what he observed.
His discovery was largely forgotten because of the plague and the civil war that followed Willibald's death on the battlefield, and only twenty-six years later Gaudecker's ape was studied more rigorously.
Emperor Wigbold's University professor of mathematics Otto-Heinrich von Lichtenfels, a noted natural scientist, was intrigued by Gaudecker's descriptions of the creatures' behavior. They were seen generally before or during a strong wind or blizzard, stalking the troops, and didn't attack unless the target was weak and isolated. Enlisting the help of a few scientists, including von Gaudecker himself, von Lichtenfels first studied the strange organ, finding it somewhat conceptually reminiscent of his own design of a device for the free transformation of work. Building upon that discovery, Lichtenfels proposed that the creature must have developed that organ as a means of survival, self-defence, and hunting, leveraging it to increase its body temperature by work transformation and simultaneously depriving the air around it of work, thus cooling it. This, Lichtenfels argued, created winds that allowed the creature to obscure iself among the snow or weaken its prey until it is safe to kill and consume it without the risk of injury. This he attempted to explain as more advantageous due to the hardship associated with mending wounds.
It is notable that the local populace generally shuns the area of Snowy Rock Mountains where the ape was discovered, citing the local legends of the evil witches that reside there, conjuring blizzards and leading travellers astray. Currently von Gaudecker's theory of cooperative hunting practices among the creatures is considered plausible, yet unproven.