In Noddist eschatology, the Last Daughter of Eve is a mortal woman, identified by a moon-shaped birthmark. She will be a critical figure in deciding the fate of all creatures during Gehenna. Various Gehenna cults spend a lot of time looking for girls who meet the Last Daughter's (admittedly vague) description.
Her title is taken to imply that before Gehenna, the human race will decline or begin to die off. Days of Fire interprets this as a precipitous drop in female fertility rates as the Time of Judgment approaches.
Several characters bearing this crescent-shaped birthmark have appeared in various sourcebooks leading up to Gehenna: