The Dead Kingdom is a novel by Geraldine Harris published in 1983.
The Dead Kingdom is the third novel of the "Seven Citadels" tetralogy.
[1] Dave Langford reviewed The Dead Kingdom for White Dwarf #62 and stated that "evidently she planned the four books as a whole rather than writing blindly into the unknown or tacking extensions onto a self-contained novel.
To all sequelholics I say, go thou and do likewise.
"[1]