Iggwilv
Iggwilv is a malevolent female archmage originating from the Greyhawk setting. She belongs to that small, elite club who represent characters originally played by Gygax and his buddies during the founding of Dungeons & Dragons, such as Murlynd, Zagyg and Mordenkainen. Her in-game lore is that she adventured with them, learning much about magic in the process, but ultimately revealed herself as evil and betrayed them, going on to become one of the Great Wheel's foremost experts on black magic and demonology. So much so that Dragon Magazine titled its articles on various demons and Demon Princes as "The Demonomicon of Iggwilv", after a literal book she wrote on the subject.
She is the mother of the cambion Iuz, who later ascended to an actual god on their homeworld of Greyhawk who she gave birth to during a period she kept the Demon Prince Graz'zt bound as her personal manservant and boytoy.
It's rumored that she may be a daughter of Baba Yaga.