If we're talking about mythology, for example, hydras shouldn't regenerate in the way they do; instead, they should regenerate in an arithmetic progression depending on the number that died, and they could only be killed, say, with fire. With vampires, it's just nonsense – who gave them the right to walk around during the day:smile24:? By the way, for reference, there is a group of diseases called porphyria – people suffering from this disease really need blood, and under the influence of sunlight, their hands and feet, or rather, the illuminated areas, curl up – so vampires really exist, but in the Middle Ages, it was all exaggerated.