Tilda Swinton is my Patronus. No, not on some Pottermore quiz, but she is the physical embodiment of the spectral being I would hope to summon to defend me from soul-sucking monsters. The British actress steals nearly every scene she’s in. She’s delivered supremely memorable appearances in genre fare like Snowpiercer and Constantine, and even managed to make sleeping in a glass box in a museum lobby seem like a worthwhile artistic endeavor. There’s a mystical quality to Tilda Swinton, which is why she seems tailor-made to tackle the role of the Ancient One in Marvel’s Doctor Strange this November.

While her casting was initially met with backlash and allegations of whitewashing—perhaps understandably so given the character’s comic book origins—Swinton seems to be doing a terrific job of making the role her own. Back in January, Nerdist and other press outlets were invited to visit the set of Doctor Strange in London, where we got to witness Swinton and her castmates in action, and interview the Ancient One about her grand entrance into the Marvel Cinematic Universe.

The moment Tilda Swinton entered the tent where members of the press were huddled around a video monitor, a chill ran across the room. Not because it was cold (it was), but because it was slightly shocking to see Swinton in her full Ancient One garb in person, shaved head and all. Although she bore no real resemblance to the character I remembered from the comics, she did seem to embody a master of the mystic arts. Given the distinct visual differences, how would Swinton be approaching this classic character?

“Well, this is the launch of the Doctor Strange film interpretation, of, in my view, a classic, which has been interpreted many times by other graphic artists. And this is just our graphic interpretation of the Ancient One,” Swinton explained to us. “I would say the whole approach is about a kind of fluidity. There are many graphic artists who have interpreted the Ancient One as a Tibetan Buddhist Lama. We’re kind of shifting that a bit… We’re trying not to be fixed to any one thing, any one gender, any one spiritual discipline, and any one race even; we’re just trying to wing it beyond that. So it’s a new gesture really, just another interpretation.”

Transforming her physical appearance was an essential part of capturing that fluidity and allowing Swinton to take on the persona of the Ancient One.

“It certainly centers everything, because we’re making shapes and these shapes are pretty rocking, they’re all pretty graphic,” Swinton said. “We’re filling a big universe, and so the look and the sort of plasticity of us is really important to us when we’re striking poses here. It’s very important, it’s really great. It’s such fun to work on. I was really lucky that Jeremy Woodhead, who’s the hair and makeup designer on this, is someone I know very well, I worked with him very closely on a Bong Joon-Ho film called Snowpiercer and we worked on making that look, and so we worked again on this and that’s been really fun. And it took its time, that’s part of the fun. The development of all of it is a ride.”

But aesthetics and personal metamorphoses aside, the real question is what kind of relationship will this incarnation of the Ancient One have with the haughty yet broken man that is Stephen Strange? The answer, it seems, not only hearkens back to the comics, but also has takes on new connotations. In this version of Doctor Strange, the characters seem to have formed a surrogate family.

“Well, the Ancient One, as you know, is the master, is the Sorcerer Supreme. And Strange comes to learn how to heal himself and the Ancient One has got the knowledge,” explained Swinton. “And so what you’re seeing today is a part of the whole training section when he’s learning the moves and digging deep. So it’s all about that, it’s all about trying to push him to get there … [We’re filming] a section when [it’s] getting to touch-and-go whether he’s gonna makes the grade. But as we know, he does. And how it progresses is, again, the story. It’s really important to the Ancient One that Doctor Strange does cut it, because the Ancient One needs a successor, or certainly needs, you could say, a son. So the Ancient One is really invested in Doctor Strange. It’s a very kind of primal relationship.”

One of the biggest challenges for both Swinton and director Scott Derrickson was finding the tonal balance between fantasy and reality. After all, if you throw the audience too far off the deep end and they might get lost in a sea of acid-fried weirdness and far-out Steve Ditko-inspired visuals.

“We started chewing this cud a while ago,” Swinton said of her conversations with Derrickson. “He is, as you probably know, an extremely erudite thinker in terms of religious philosophy and just thinking about a modern take on something really, really ancient, about how to imagine living beyond any physical bounds, which we’re on the verge of now. I mean, I was just talking to Benedict [Cumberbatch], who’s got a little baby [who] knows his father lives in his phone. We as humans are evolving really fast, so everyday we’re hit with that. This film kind of takes that everyday boring reality and really bursts it wide. So we talked a lot about that. In many ways there’s something very practical about this world, the Kamar-Taj. You know, we all look like samurai warriors, but actually there are iPads everywhere and there’s a feeling that it’s a practical possibility for this modern world that the Doctor Strange universe is functioning, and that we know it and it’s around the corner for all of us. So we talked about that. We talked about making it kind of muscular and practical. Yeah, it’s a fantasy, but what’s the difference between fantasy and reality, really?”

But just because they’re putting a new spin on a character like the Ancient One doesn’t mean that Swinton or the filmmakers have any disrespect for the source material. Quite the opposite actually, Swinton assured us.

“The comics are—I mean, that’s the root. That’s the source,” Swinton said. “As I said, it’s just another interpretation. One of the wonderful things that I’ve always loved as an art student, what I always loved about comics, was that they are interpreted differently by different graphic artists all the time. So now film is doing that, thanks to Marvel Studios. I’m a huge Marvel fan and the fact that they take the liberties that they do in filmmaking I think, if anything, that it dignifies the comics and it says, ‘Yeah. This is a strong enough, robust enough source. We can bend it, it’s elastic. It’s bouncy.’”

In fact, according to Swinton, this film is going to push the MCU to a place we’ve never seen it before.

“Even in terms of the Marvel Universe, this is going on a side street into a major piazza that Marvel hasn’t even been to before, because it’s all about creation and not so much about destruction and forestalling destruction; it’s about your mind,” she explained. “This is a huge, great story about the possibility of living beyond everything, living beyond mortality, living beyond all the immortal confines, living beyond the planet as we know it. It’s mind-blowingly no-limits, and I think this is going to be something else.”

Doctor Strange hits theaters on November 4, 2016.

Everything you need to know about Doctor Strange

Read our complete set visit report, featuring interviews with Benedict Cumberbatch, Kevin Feige, Scott Derrickson, and Benedict Wong!

For high-res, full-size behind-the-scenes images and new character posters, please click to enlarge in our gallery below.

Image: Disney/Marvel

Dan Casey is the senior editor of Nerdist and the author of books about Star Wars and the Avengers. Follow him on Twitter (@Osteoferocious).