Castle Mordo is the ancestral home of the Mordo family. It is located in the town of Varf Mandra in Transylvania. Its earliest known family member was Viscount Heinrich Crowler. Before World War I, the lands surrounding Transylvania fell under the control of the Austrio-Hungarian Empire and the family nobleman Nikolai Mordo earned the title of Baron. Nikolai and his wife Sara Crowler-Mordo (the daughter of Viscount Crowler) gave birth to a son, Karl Amadeus Mordo in 1921.
Desiring to wrest the secrets of black magic from his master The Ancient One, Baron Mordo entered a trance to visit him in astral form and poison him by controlling his servant. Confronted by Doctor Strange, he fled to his body and lost control over the master's servant. Strange followed him in astral form and told him Mordo that his plot had failed.
On Earth-9047, the castle of Baron Mordodo -Mordo's analogue in that reality- is on Tibet and has guided tours. Although there is a McMordodo's restaurant within the castle itself, Mordodo prefers home delivery pizza, which is difficult to obtain at his home and at useemly hours.