There was no widespread belief in werewolves in medieval Europe before the 14th century. There were some examples of man-wolf transformations in the court literature of the time. Liutprand of Cremona reports a rumour that Bajan, son of Simeon I of Bulgaria, could use magic to turn himself into a wolf. Marie de France's poem Bisclavret (c. 1200), in which the nobleman Bizuneh, for reasons not described, had to transform into a wolf every week. When his treacherous wife stole his clothing needed to restore his human form, he escaped the king's wolf hunt by imploring the king for mercy and accompanied the king thereafter. His behaviour at court was so much gentler than when his wife and her new husband appeared at court, that his hateful attack on the couple was deemed justly motivated, and the truth was revealed.
The German word werwolf is recorded by Burchard von Worms in the 11th century, and by Bertold of Regensburg in the 13th, but is not recorded in all of medieval German poetry or fiction. References to werewolves are also rare in England, presumably because whatever significance the "wolf-men" of Germanic paganism had carried, the associated beliefs and practices had been successfully repressed after Christianization (or if they persisted, they did so outside of the sphere of literacy available to us). In 1539, Martin Luther used the form beerwolf to describe a hypothetical ruler worse than a tyrant who must be resisted.
The Germanic pagan traditions associated with wolf-men persisted longest in the Scandinavian Viking Age. Harald I of Norway is known to have had a body of Úlfhednar (wolf coated [men]), which are mentioned in the Vatnsdœla saga, Haraldskvæði, and the Völsunga saga, and resemble some werewolf legends. The Úlfhednar were fighters similar to the berserkers, though they dressed in wolf hides rather than those of bears and were reputed to channel the spirits of these animals to enhance effectiveness in battle. These warriors were resistant to pain and killed viciously in battle, much like wild animals. Úlfhednar and berserkers are closely associated with the Norse god Odin.
The Scandinavian traditions of this period may have spread to Kievan Rus', giving rise to the Slavic "werewolf" tales. The 11th-century Belarusian Prince Vseslav of Polatsk was considered to have been a Werewolf, capable of moving at superhuman speeds, as recounted in The Tale of Igor's Campaign:
"Vseslav the prince judged men; as prince, he ruled towns; but at night he prowled in the guise of a wolf. From Kiev, prowling, he reached, before the cocks crew, Tmutorokan. The path of Great Sun, as a wolf, prowling, he crossed. For him in Polotsk they rang for matins early at St. Sophia the bells; but he heard the ringing in Kiev."
The situation as described during the medieval period gives rise to the dual form of werewolf folklore in Early Modern Europe. On one hand the "Germanic" werewolf, which becomes associated with the witchcraft panic from around 1400, and on the other hand the "Slavic" werewolf or vlkolak, which becomes associated with the concept of the revenant or "vampire". The "eastern" werewolf-vampire is found in the folklore of Central and Eastern Europe, including Hungary, Romania and the Balkans, while the "western" werewolf-sorcerer is found in France, German-speaking Europe and in the Baltic.
