Who is Sidewinder? Marvel star Giancarlo Esposito explains ‘Captain America’ villain

For weeks, Marvel fans wondered who the heck Giancarlo Esposito, the beloved actor from Breaking Bad and The Boys, was playing in Captain America: Brave New World. He was surprise revealed as a new character for the Anthony Mackie-led film that was added through reshoots. Paparazzi captured photos of Esposito on set wearing a black, militarized vest and shades, while wielding an automatic rifle and looking generally badass. But it was only on the Hall H stage at Comic-Con in San Diego Saturday that his character was officially revealed.

“Can I say it? Wow! I can finally unleash it. I am the King of the Serpent Society. I am Sidewinder!” Esposito declared before an energized crowd of fans.

The figure isn’t a household name among mainstream audiences not well versed in the lore of Marvel Comics. So who is Sidewinder? What are his aims? How is he different in the context of the Marvel Cinematic Universe? Esposito tells Entertainment Weekly about his nefarious character coming to Captain America: Brave New World, in theaters this Feb. 14, 2025.

Who is Sidewinder?

Sidewinder has a pretty unique look in Marvel comics that doesn’t quite work so well in the more grounded world of Captain America: red mask, snake-like armor, a sweeping cloak, and reptilian neck piece.

His real name is Seth Voelker, who was dismissed from his old position as a college professor. Seth was hired by the Roxxon Oil Company to perform criminal acts, which would include stealing a rare mystical artifact called the Serpent Crown that’s linked to the god known as Set, granting the wearer magical abilities like mind control and immortality.

The president of Roxxon gave Seth leadership of the Serpent Squad, a villain group of snake-themed characters. Seth took the name Sidewinder, with his special cloak that allowed him to teleport. Sidewinder later reformed the Serpent Squad into the Serpent Society, turning them into one of the world’s most nefarious team of mercenaries. Members included Black Mamba, Death Adder, Anaconda, Asp, Cottonmouth, Diamondback, Princess Python, Rattler, and Viper.

The Serpent Society’s MCU history

In 2014, Marvel Studios set up an epic fan event out of the El Capitan Theatre in Hollywood, where they announced all the films coming for Phase 3 of the MCU, including Chadwick Boseman‘s casting as Black Panther and what was originally set to be a two-part Avengers: Infinity War movie that would later be broken up into Avengers: Infinity War and Avengers: Endgame.

At the start of the festivities, Marvel head Kevin Feige threw everyone for a loop by revealing the third Cap entry to be Captain America: Serpent Society. It wasn’t completely out of the realm of possibility, given how the villain group was originally comprised of members hellbent on tainting Cap’s good name. But Feige, much later in that event, basically went “just kidding” and confirmed the real title as Captain America: Civil War.

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“We had this great idea because Civil War‘s first up, right? But we don’t blow our wad on the presentation with Civil War right at the front of it,” Feige explained at the time of the fake-out during a Q&A with reporters at the event. “[Late Marvel marketing and publicity executive] Mike Pasciullo had the idea to put Serpent Society on there, and I thought it was awesome and hilarious. A part of me thought, ‘Are people going to love Serpent Society and think that’d be really cool?'”

How does Esposito feel now that Sidewinder and the Serpent Society are officially entering the MCU with Captain America: Brave New World? “I think there’s such great, creative minds in the MCU that have decided to go back in the great cycle of comics to create Seth Voelker and the Serpent Society,” he tells EW.

Who is the Sidewinder of the MCU?

It seems clear that at least some elements of the comic-book Sidewinder will be changed for the MCU, if we’re talking about Esposito’s costume alone. But the actor gives a little tease of the role beyond the look to EW.

“I like it because he’s a complicated guy who didn’t start in a nefarious way,” Esposito explains. “He came to this in a different way, which hopefully will unfold. I like it for me because you’ve seen me play certain villainous characters who use their brain, who are great at dictating what to do and how to do it.” Those roles have included Gus Fring on Breaking Bad and Better Call Saul, Stan Edgar on The Boys, Moff Gideon on The Mandalorian, and Lex Luthor on Harley Quinn. Sidewinder, however, is not so much that.

“I like Sidewinder because he’s a physical guy,” Esposito continues. “He’s got to go toe-to-toe with his physicality and he knows how to use the tools of his trade. So he’s someone who plays against some of the things in the comic that you may think could be true.”

Captain America: Brave New World, directed by Julius Onah, sees Sam Wilson (Anthony Mackie), the new Cap, in the midst of an international incident. After President Thaddeus “Thunderbolt” Ross (Harrison Ford) becomes the target of an assassination attempt involving brainwashed Super Soldiers, including Isaiah Bradley (The Falcon and the Winter Soldier star Carl Lumbly), Sam discovers Ross’ inner circle has been compromised and there’s a global catastrophe he must solve.

The cast includes Tim Blake Nelson returning as Samuel Sterns from The Incredible Hulk; Shira Haas playing Ruth Bat-Seraph, an Israeli former Black Widow who’s now a U.S. government official; Xosha Roquemore as a member of Ross’ security team; and Liv Tyler, another face from The Incredible Hulk, returning as Ross’ daughter Betty.

Watch the full interview with the cast of Captain America: Brave New World in the video above.