The younger sister of the Vampire Lord Count Reiner Heydrich, Katarina Heydrich is a major antagonist in Vault of the Vampire and Revenge of the Vampire; the two Fighting Fantasy gamebooks that feature her brother as the main villain, especially in the first one. Katarina is a very powerful and beautiful witch, somehow based on the infamous child-murderer Countess Ersébeth Bathory, as she uses the blood of youngsters to remain young.