Changelings
Anne McCaffrey & Elizabeth Ann Scarborough
Twins of Petaybee (1)
They do it with mirrors
Agatha Christie
Miss Marple (6)
Rise of Tiamat
Wizards of the Coast
Sport of Queens
Dick Francis
Sir Gawain and the Green Knight, Pearl, and Sir Orfeo
J. R. R. Tolkien
The Adventures of Tom Bombadil