The Unknown Witches of Oz: Locasta and the Three Adepts is a modern Oz novel, written by David Hardenbrook and illustrated by Kerry Rouleau. It was published in 2000 by Galde Press; its publication was timed to coincide with the centennial of The Wonderful Wizard of Oz (as was also true of Edward Einhorn's Paradox in Oz and Gina Wickwar's The Hidden Prince of Oz).
In Hardenbrook's plot, Locasta, the Good Witch of the North, has been forced out of Oz by Mombi, and ends up in Los Angeles; she makes her way back to Oz with the help of a sixteen-year-old named Dan. Locasta joins with Ozma and Glinda to defeat Mombi, the Nome King, and other nemeses. In an extreme departure from the practice of conventional Oz literature, Hardenbrook makes his hero Dan a romantic interest for Ozma.
Hardenbrook drew upon wide-ranging hints and inspirations in L. Frank Baum's canon for his book. Locasta is the name that Baum gave to the in his original 1902 musical adaptation of his classic book. The Three Adepts come from Baum's final Oz book, Glinda of Oz, though Hardenbrook gives them new names and identities, making them Locasta's granddaughters.
This book is the opening volume in a projected Oz trilogy, called Dan in Oz. The trilogy's second book, Jellia Jamb, Maid of Oz, was published in 2008.
Hardenbrook goes farther than most Oz authors have done in his attempt to construct a conceptual framework for the fantasy realm of Oz. His Oz is in a parallel universe, in "a galaxy very like our own Milky Way" where "a star virtually identical to our sun" has "a planet that corresponds to Earth...." (This planet, however, has two moons and "a polychromatic ring system....") Among this Earth's continents and archipelagoes is "Baumgea," corresponding to Nonestica, along with other exotic locales like "Geiselea" and "Dodgesonia."