Elves were mythical creatures. The term was sometimes used interchangeably with "fairy" to refer to members of the Fair Folk or Sidhe, (PROSE: Autumn Mist) but could also refer to quite distinctive creatures, such as "Santa's little helpers". (PROSE: Autumn Mist, TV: Last Christmas, etc.)
The First Doctor encountered elves and dwarves on Elbyon. (PROSE: The Sorcerer's Apprentice)
The True History of Planets was a book about elves and magic until it was rewritten as a text to support a revolution on dogworld. (PROSE: Mad Dogs and Englishmen)
Caligaris Epsilon Six was a holiday planet that was designed and constructed to resemble a fantastic medieval European version of Earth. It had genetically engineered elves, cyborg dragons and robotic fairies. (COMIC: A Fairytale Life)
In a shared dream induced by the Kantrofarri, the elves Ian and the Wolf acted as helpers for Santa Claus, aiding him in delivering Christmas presents. (TV: Last Christmas)
The term "elf" was considered racist by elves when used by non-elves, Ian debated about the term's offensiveness with Santa Claus. (PROSE: Ian the Elf)
Mirkwood was a forest where elves lived. Giant spiders and an evil wizard were found there, but the Thirteenth Doctor admitted she usually only remembered the elves. (PROSE: Molten Heart)