After designing costumes for four Marvel movies (Thor, The Avengers, Guardians of the Galaxy, Avengers: Age of Ultron), putting together a superhero costume is old hat for Alexandra Byrne. But the woman who won an Oscar for Elizabeth: The Golden Age found her work on Marvel’s latest a little, well, strange. Never mind having to design costumes for a story that spans the globe and multiple dimensions. Forget having to clothe Tilda Swinton, Marvel’s most fashion-forward star yet. The real challenge of Doctor Strange was Benedict Cumberbatch’s iconic red cloak you’ve seen so much of. Byrne has designed plenty of red cloaks before (hello, Thor!), but this one was a particular challenge. Because, though you may not know it yet, that cloak is secretly the most delightful part of Doctor Strange.

The thick, red asymmetrical garment (better known as the Cloak of Levitation to Marvel experts) required an entire team of costumers whose work resulted in, Byrne estimates, 12 finished versions. But after the costume team had their way with it, the cloak got a C.G. version as well. Yes, this article of clothing has a mind of its own—think the flying carpet sidekick in Aladdin—and serves as Strange’s constant companion and comic relief. The edges of his collar wipe away tears, it physically restrains Strange from making bad decisions, and stretches the boundaries of what we’ve seen from a live-action garment.

The cloak also comes with the burden of a tremendous amount of comic-book-lover expectations. “It has huge history and expectations,” Byrne admits. “I wanted very much the flavor of the cloak and Strange’s costume to be not over-embellished and decorative, but for the detail to be subtle and draw you into the costume the way it draws you into the comic books. On the cloak, we go from hand embroidery to flocking to printing to machine embroidery to all kinds of finishes in the one piece.”

Courtesy of Marvel

But some of the details on that cloak were definitely more practical than decorative. The delicate mosaic clasps at the base of Strange’s collar actually magnetically lock the cloak into place to avoid costume-related injury to Cumberbatch in action scenes. “There’s a harness underneath that the cloak is locked, which very well-fitted to the body so that you’re not worried about swerving around the neck and then strangling him and all that.”

And Doctor Strange couldn’t coast on that cloak alone. Cumberbatch’s main deep-blue costume—which Byrne created the most duplicates of—shows off the Asian influence on the film’s design. “One of the key starting points was was a child’s Chinese coat that we found that was made of indigo fabrics, and for warmth, it was made of 10 layers that were all offset of indigo cotton. They all had a slightly different color, but the way the things were all laid on top of each other, it gave it sort of a strange quality and a bulk. That was a very key moment.”

And as for other-worldly influences on design, Byrne admits she had to consider *Doctor Strange’*s trippier elements when picking her colors and shapes: “Knowing that Strange would have to exist in all these incredibly psychedelic environments. He needed to have a very strong silhouette that would hold in these incredible Steve Ditko–inspired landscapes.”

Tilda Swinton was able to lend her fashion expertise in crafting the style of the Ancient One. The collaborative process, Byrne says, resulted in a stunning progression of robes that drew inspiration from Asian clothing, couture, and catwalk. “Obviously we wanted a very androgynous body for her,” Byrne explains. “That influenced certainly where the belt sat and how she was standing and things like that.”

As Byrne knows well after working for Marvel this long, when you design one Avengers film, you have to keep an eye on the inevitable superhero mash-up. “When it’s an origins story, your first challenge is to make the character work,” Byrne says. But having completed five films in the Avengers franchise, she admits she has an “instinctive feel” for how all the styles will blend together. “I did the first Avengers, which was when the characters began to come together. Maybe having done that, you have the faith in knowing that it can work.”

But Byrne can offer up one hint about Strange’s future travels. It wouldn’t be a Marvel movie if it didn’t end with at least one cameo, and we see at the very end of Doctor Strange just how well Cumberbatch’s crimson cape will measure up against another famous one. “Doctor Strange, the first time we end this film, he is the sorcerer supreme, so we see him briefly at the end of the film in his master’s robes, which we haven’t seen before,” Byrne reveals. “That is the nod towards where he’s going to go next.”