In Terry Pratchett's Discworld novels, elves are of a race that lived before the Iron Age, and were banished by steel weapons. Elves on the Discworld are based on the nastier kind of fairy-folk in European (and other) folklores than elves as portrayed in most modern (post-Tolkien) fantasy fiction. They are native to the Disc, but now live in a parallel world, sometimes called Fairyland. During certain times of the year, such as Mid-Summer, the walls between Fairyland and ordinary reality become thin, allowing the elves (and other fae creatures such as unicorns, Jenny Greenteeth and, before they were cast out, the Nac Mac Feegle) to break through.