WARNING: The following article contains spoilers for Marvel's Avengers: Infinity War, in theaters now.

In a blockbuster filled with surprising deaths and disappearances, the least-expected development in Avengers: Infinity War may have been the return of a character who hadn't been seen in the Marvel Cinematic Universe since 2011: the Red Skull.

After all, the classic villain seemingly died in Captain America: The First Avenger when he held the damaged Tesseract, containing the Soul Stone. However, Infinity War confirmed the theory that the Red Skull hadn't been killed, but rather transported by a wormhole through space to the planet Vormir, where he's remained the guardian of the Soul Stone for the past seven decades.

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Speaking with Uproxx, Infinity War directors Joe and Anthony Russo explained they chose the Red Skull because they wanted a character who could credibly tell Thanos and Gamora the rules for acquiring the Soul Stone.

"[T]he Red Skull has been turned into this wraith who now guards the Soul Stone and distributes the rules to whoever shows up there trying to obtain it," Joe Russo said. "It felt like there was more credibility than just a random character."

"Somebody who has history with the stones may seem like they have a little more authority in terms of their experience -- especially a tragic experience," added Anthony Russo.

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For that task, the Russos turned not to Hugo Weaving, who stated as far back as 2012 that he had no interest in returning to the character, but rather The Walking Dead actor Ross Marquand.

"Ross Marquand did an incredible job of capturing not only the essence of his voice, but the essence of his performance -- a haunted figure who is now this imprisoned spirit," Joe Russo said.

In theaters now, Avengers: Infinity War stars Robert Downey Jr., Chris Evans, Chris Hemsworth, Mark Ruffalo, Jeremy Renner, Scarlett Johansson, Anthony Mackie, Paul Rudd, Elizabeth Olsen, Tom Holland, Benedict Cumberbatch, Chadwick Boseman, Chris Pratt, Zoe Saldana, Dave Bautista, Bradley Cooper, Vin Diesel, Tom Hiddleston, and Josh Brolin.