Once upon a time, the high priest Kha Semblor had the king of Stygia murdered, and was in turn slain by the king's sister Nitocris. Hundreds of years later, Conan meets the witch Sabbatha and her daughter Rosina, who both share an unhealty affection for some magic artifacts, a diamond and a set of crystal miniature figurines. Rosina and the artifacts are taken by the sibling magicians Stornella and Valvaxier, who are planning to use their magic to replace the queen of Stygia. The crystal miniatures come alive, and Conan and Rosina barely escape death.