Despite early rumors about his potential cameo in Avengers: Infinity War, the reintroduction of the Red Skull in the Marvel Studios blockbuster still managed to surprise. Last seen in 2011's Captain America: The First Avenger, when he was seemingly killed in an explosive blast by the Tesseract, the classic villain had instead spent the past seven decades on the far-flung planet Vormir as punishment for his misuse of the Soul Stone. Referred to now as the Stonekeeper, the hooded figure remained, after all those years, still recognizable as the Red Skull. However, that wasn't always the case.

The newly released Marvel's Avengers: Infinity War -- The Art of the Movie showcases some 67 early concepts for the Stonekeeper, of which only a relative handful resemble how he appears in the film -- or, for that matter, resemble Captain America's archenemy at all.

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Some of the illustrations show a weathered Red Skull clad in a tattered version of his uniform from The First Avenger. With others, we could be forgiven for mistaking him for the Fantastic Four's nemesis, Doctor Doom. In some, Johann Schmidt's signature crimson pigment had turned chalk white, and when paired with a tattered hooded cloak, he appeared much like DC's Spectre.

"I designed versions hiding his face and versions showing how much life or soul the stone took from him," concept artist Rodney Fuentebella recalls in the book. "I want to play with the idea of what the Soul Stone had done to him and whether he is a ghostlike being now or something soulless."

Illustrations by Jerad Marantz, from Marvel's Avengers: Infinity War -- The Art of the Movie

Arguably the most striking, and definitely the most nightmarish, conceptions of the Stonekeeper are those by Jerad Marantz, which transform the former Red Skull into something inhuman. In the illustrations at top, the Marvel Cinematic Universe villain may evoke the Pale Man from Guillermo del Toro's Pan's Labyrinth, and at bottom, a more insidious Dr. Finkelstein from The Nightmare Before Christmas.

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In both, the Red Skull has lost his eyes, although whether that would have been from the explosion in The First Avenger or as punishment for his abuse of the Soul Stone isn't specified.

"The idea of really hollowing him out and embracing the more horrific aspects of his look was something I took a lot of delight in exploring," concept artist Ian Joyner relates in Marvel's Avengers: Infinity War -- The Art of the Movie.

The still-untitled sequel to Infinity War arrives May 3, 2019. Directed by Joe and Anthony Russo, Marvel’s Avengers 4 stars Robert Downey Jr., Josh Brolin, Mark Ruffalo, Tom Hiddleston, Chris Evans, Chris Hemsworth, Jeremy Renner, Chris Pratt, Elizabeth Olsen, Sebastian Stan, Benedict Cumberbatch, Paul Bettany, Samuel L. Jackson, Cobie Smulders, Benedict Wong, Zoe Saldana, Karen Gillan, Vin Diesel, Dave Bautista, Pom Klementieff, Scarlett Johansson, Tom Holland and Anthony Mackie.