The Maid is a mysterious young woman who appears in The Bones of Makaidos in the Valley of Lost Souls. She has a French accent and acts as a mentor and swordsmaster to Sapphira Adi and Bonnie Silver when they are trapped in the Valley of Lost Souls for four years in preparation for their final battle against Devin and Morgan.
The Maid has waist length blond hair, and wears a brown tunic on top of a white dress, with a sword scabbard on her belt. She is described as blond, lithe, and beautiful, with a peaceful joyous face. And she is usually engulfed in a fiery aura.
It is possible that she is meant to be Joan of Arc, who called herself "The Maid," wore white, served or claimed to serve God, was French, and knew how to wield a sword.