In Lord of the Rings movie by Peter Jackson Nazgûls are depicted as phantoms in black cloaks with swords often riding on horses:
What did Peter Jackson take as a base (prototype) to build the character images for his movies' Nazgûls?
I'm not sure how Nazgûls were depicted in J.Tolkien's novel and whether there are original illustrations avaiabale somewhere.
Some similarities have the character images of Dementors from Harry Potter film series:
Similar character image has also the Death on the Pale Horse (one of the four horsemens) from the Bible's
Question: Where do character images (appearance) of Nazguls from LOTR originate from? Did Peter Jackson take it from original Tolkien's illustrations (if they exist) or he constructed it based on some prototype?