This world is the same as ours. Pretty much. Physical geography coincides completely. Political is a little different from our Middle Ages. Not too important. Technological progress was similar. Not exactly, so rivets on the topic of correspondence to the era are not accepted. The fundamental difference is one. A person has a recessive gene. Full-fledged carriers of this gene can change their appearance at will. No, they don't become wolves or bears. Facial features do not change very much. But fangs appear, claws capable of tearing the best steel, short hair on the body. At the same time, werewolves become much faster and stronger. Including speed considerations. All skills acquired by a person are preserved in Appearance. They are called differently in different countries: forklifts, berserkers, velets... In some places they do not name. And in some places they are not at all. And they relate in different ways. Someone saves, someone uses. And some people consider evil spirits. But they are what they are.