Cats of Queen Berúthiel
Cats of Queen Berúthiel were the cats of Queen Berúthiel, the wife of Tarannon Falastur, twelfth King of Gondor.
Overview
In The Lord of the Rings, Aragorn uses the cats as a byword for navigation in the dark: Gandalf is surer of finding the way home in a blind night than the cats of Queen Berúthiel.
The cats of Queen Berúthiel were mentioned by Tolkien in a 1956 letter as only one of the two references (besides the names of the Blue Wizards) in the whole Lord of the Rings that does not actually exists, on its own plane (of secondary or sub-creational reality.) Before the publication of the Unfinished Tales, the cats were (in the words of Christopher Tolkien) "hitherto wholly mysterious."
According to Unfinished Tales, Queen Berúthiel had nine cats. The cats were her slaves whom she used as spies "to discover all the dark secrets of Gondor."
Queen Berúthiel was feared and reviled in Gondor, and at last her husband the King banished her from the realm. She was last seen aboard a ship, with all her cats, sailing away into the southern seas.
Many things have been written about the cats of Queen Berúthiel. For example the following: "Tolkien spent years creating his world, and it shows, in what he reveals and also what he merely hints at. For instance, there are the famous 'cats of Queen Beruthiel', the subject of an off-hand comment by Aragorn—we never find out anything more about the cats or their mistress, but just the mention of them suggests, as Tom Shippey says in his excellent J.R.R. Tolkien: Author of the Century, 'that there is a world outside the story'.