Not a legend, but a real mystery (more than 100 victim, mostly children and women : one of the first know psycho-serial killer IMO), who became a legend. Here is one of the many link about the beast : http://www.tao-yin.com/bete-gevaudan/SpikeyFreak said:
From what I understand, the film is losely based on either a book, play or other movie that is losely based on a French legend.
--Spikey du Loup