If the trailers are anything to go by, we already know where to find fantastic beasts: Eddie Redmayne has a suitcase full of them in 1926 New York. But where did they come from, the dragons, unicorns and hippogriffs of the Harry Potter universe? Monsters and mythical beasts perform a role in JK Rowling’s work which transcends that of world-building: they add symbolic and psychological depth, as well as reminding us that we are visiting a magical place. Rowling is both an inventor and archivist of fantastical animals, populating her universe with a mixture of what one might term ‘classic monsters’ (trolls, centaurs, mer-people) and folklore staples (bowtruckles, erklings), alongside her own inventions (dementors).
article de Natalie Haynes : http://www.bbc.com/culture/story/20161122-the-myths-and-folktales-behind-harry-potter?ocid=fbcul