Teodora Heterodyne (nee Vodenicharova) was the wife of Saturnus Heterodyne, mother of William and Barry Heterodyne, and thus grandmother of Agatha. To date she has only been mentioned in The Secret Blueprints (where she is not even named), and in a footnote in the novel Agatha H. and the Voice of the Castle, and so all information presented here should be considered tentative.