Mephista
In Reality Z-25 31-H, Mephista was a demoness and the consort of the Devil. She appeared as a woman with pale skin, long jet-black hair, pointed ears, small horns and equally diminutive bat-like wings. She was usually completed naked, although her long hair partially covered her chest.
Mephista cheated on the Devil with Armstrong Fatbuckle, the “Worst Man in the World”, shortly after he died. The Devil caught them in the act and, in anger, banished Armstrong from Hell, causing him to return to the world of the living as an undead skeleton. Some time later, Mephista told the story of Armstrong Fatbuckle to an unknown audience of “surface-dwellers”. (COMIC: Hell Is Too Good For Him)
Some time later, when Kelly made a deal with the Devil for the recently-dead Jenkins to be returned to life, Mephista went to fetch him. (COMIC: Journey Out Of Misery)
Behind the scenes
Mephista's name is a feminised version of that of the notorious demon Mephisto.