One of the biggest villains in the Doctor Strange comics is Karl Mordo, a sorcerer who, like Stephen Strange, is mentored by the Tibet-dwelling Ancient One, but who ultimately turns evil. Is the Mordo who audiences will see Chiwetel Ejiofor portray in the Benedict Cumberbatch-starring Doctor Strange (out Nov. 4) similarly bad? How exactly would the 12 Years a Slave star describe his character’s relationship with the Tilda Swinton-played Ancient One?

“In terms of his life with the Ancient One, it’s this long and intense relationship they have that’s just very deep and very connected,” says Ejiofor. “I think they both recognize in Strange this certain quality that they feel is going to be very useful in a situation they’re in — just by the nature of who he is, and the way that he operates, and the way his mind works, and the certain skill set and personality that he has. So, when they all meet, they realize that he’s somebody that can be plugged into this very surreal, interesting, sort of fascinating circumstance that they’re all in, and the dangers that they face. And so it becomes a process of assimilating him into their ways of life.”