The Lord of Nightmares/L-sama (Slayers) is beyond meaningless concepts such as good or evil, male or female, and mortal or immortal. (S)he simply is what (s)he is.
As a unique creation of the gods, Enkidu (TYPE-MOON) cannot be classified under such simple terms as male or female, human or beast, god or demon, Enkidu's appearance and form transcend those meaningless concepts.
Because desire knows no gender, Desire of the Endless (DC/Vertigo) is both and neither gender.
Mirror Maiden (Valkyrie Crusade) has no permanent nor actual true form, and thus has no true gender at all.