The egomaniacal sorcerer Baron Karl Amadeus Mordo has let his villainous nature come through ever since the Ancient One chose Stephen Strange over him as a prized student.
Baron Mordo | Marvel 101
Born in Transylvania, Karl Mordo became a student of the Ancient one, but found defeat at the hands of Stephen Strange.
Fueled by rage and ego, Baron Mordo allies himself with individuals of questionable quality to exact vengeance on his rival Doctor Strange. Along the way, he's come close to defeating his nemesis but usually fails because of his arrogance.