The Shadow King, previously The Reluctant King, is a working title for a novel Marion Zimmer Bradley began work on before her death.
Deborah J. Ross wrote:
Marion's partial manuscript, which she had entitled The Shadow King. At one point, she was going to rewrite World Wreckers and call it The Reluctant King, just as Sword of Aldones became Sharra's Exile. The Trust agrees with me that it is better to go forward than look back at a book written so long ago. We aren't sure of the final title, except that it will be neither The Reluctant King nor The Shadow King. Its working title is only a place marker until its true name emerges. And yes, it does follow Regis, Linnea, Danilo and other characters in the years between World Wreckers and Exile's Song. The rough draft is about 1/3 done, and there is still lots more of Marion's text to work with.