Daughter of the Night by Richard S. Shaver, Science Fiction, Adventure, Fantasy (Hardcover) (ISBN-13: 9781463899158)

Like a flash of light the gleaming sword swept down. A fraction of a second later a portion of it no longer gleamed: it was crimson! And Queen Dionaea's head bounced down the stairway into her garden of live oaks. A few seconds of thought remained to it before it would be very dead; but her thought was confused by shock -- her eyes rolled uncontrollably while she tried to remember some cantrap or rune from her long association with the Goddess Diana. Desperately she tried to recite the proper abracadabra to stay the swift death that was sweeping through her mind; but it is hard for a head to chant a charm with no body to draw a breath. . . .