Kaecilius is a Marvel Comics character that appears as the main antagonist in the 2016 Marvel Studios film, Doctor Strange. He is a former student of the Ancient One. However, after becoming disillusioned by her teachings, Kaecilius left the order of the Mystic Arts and founded his own group of Zealots, determined to defeat the Ancient One and bring immortality to the world by bringing the Dark Dimension to Earth. Kaecilius was created by Stan Lee and Steve Ditko.