A common motif in fiction is that the ability to use magic is innate and often rare, or gained through a large amount of study and practice.[1]:616 In J. R. R. Tolkien's Middle-earth, it is mostly limited to non-humans, though some people gain small amounts and become known as sorcerers (wizards being powerful spirits).[citation needed] In many writers' works, it is reserved for a select group of humans,[citation needed] such as in J. K. Rowling's Harry Potter books, Katherine Kurtz's Deryni novels, or Randall Garrett's Lord Darcy universe.