The fifth book of Piers Anthony's Incarnations of Immortality series follows Orb Kaftan, a musician whose songs carry literal magic, as she searches for the Llano — a legendary piece of music said to be the most potent magic in existence. Along the way she teaches a blind Gypsy girl to sing, falls for a man who turns out to be the newly-appointed Incarnation of War, and finds herself pregnant and alone.
Her quest for the Llano's final movement, the Song of Chaos, draws the attention of a rival musician, Natasha — who is revealed to be Satan himself, courting her under an agreement with Fate that binds him to lie about everything except his eventual marriage proposal. When Orb sings the Song of Chaos to complete her power and become Gaea, Incarnation of Nature, the result is global devastation, forcing the other Incarnations to bargain with Satan himself to undo it.
Blending music, myth, and theology into Anthony's signature pun-laced fantasy, Being a Green Mother closes with Orb's reluctant, self-sacrificing bargain with the Devil — sealing her fate as Mother Nature.