You ask why I have these big hands, my friend? Well, I'll tell you my secret: exercise.
— Big Bad Wolf
The Big Bad Wolf who lived in the Land of a Thousand Fables was, like the other denizens of that strange sphere, created by Artorius Vigo based on a figure from folk tales. Once he served as a playmate to the duke's daughters, acting out scenes with a certain red-hooded girl and her grandmother, but as the fable land slowly degenerated, so did he.
Geralt and Syanna met the Big Bad Wolf while he was nursing a nasty hangover and was not eager to cooperate. Yet since our heroes needed a bean which the wolf had, they forced him to act out his tale.
That tale ended as it always had: the Big Bad Wolf attacked the Hunter (played by Geralt), biting and clawing him fiercely while his own wounds healed almost instantaneously. Inevitably, however, the Big Bad Wolf was killed and his stomach cut open.
This time, out came not a grandma and her granddaughter, but a magic bean.
The Big Bad Wolf is a reference to the fictional character, Big Bad Wolf, who appears in numerous fairy tales and nursery rhymes.
Although looking and acting almost like a common in-game werewolf, it is classified as a Beast and not as a Cursed one; this because in the fable the wolf is an actual (albeit smart and cunning) wolf and not a transformed human.