Avengers: Endgame had a Herculean task in front of it when writers Christopher Markus and Stephen McFeely were assembling the film for Marvel Studios. They had to bring in every corner of the Marvel Cinematic Universe from Thor's Asgardian realm to the Guardians of the Galaxy, not to mention every Earth-bound hero that hadn't met before the film. Furthermore, given the time travel hook of the film, there was plenty of opportunities to bring back characters and places and integrate them into the story in unexpected ways, including some villains.
Among the aliens that fought alongside Thanos in the final battle of the film are the gigantic, floating serpents of space, the Leviathans as ridden by the Chitauri and first seen in 2012's The Avengers. These creatures return for the fight with one of them getting decked by Ant-Man in the starting minutes of the battle. As the film was in the planning stages, these aliens almost got a major upgrade for the battle with Earth's Mightiest heroes.
As seen in the pages of Avengers: Endgame - The Art of the Movie, alternate designs for the Leviathans can be seen which make some radical changes. Among the potential new designs for the creatures were versions that walked on giant legs and had even bigger arms swinging by their sides, a major alteration from the non-appendaged versions that simple floated beforehand. Another version walked on four giant legs with two smaller arms sticking out of the front, and another still appeared to take its cues from the sandworms of Dune.
"These are variants of the Chitauri leviathan," concept artist Tully Summers said. "They wanted something large and seemingly insurmountable to arrive and threaten our heroes during the climactic battle. The one with drills was meant to swim through the earth and attack from underground. In the end they decided the Godzilla-sized leviathan was a tad too insurmountable and went with much smaller designs that were easier to defeat."
Avengers: Endgame is now streaming on Disney+. Avengers: Endgame - The Art of the Movie out now and can be purchased by clicking here.
Upcoming Marvel Studios projects include Black Widow on May 1, 2020, The Falcon and The Winter Soldier in Fall of 2020, The Eternals on November 6, 2020, Shang-Chi and the Legend of the Ten Rings on February 12, 2021, WandaVision in Spring 2021, Loki in Spring 2021, Doctor Strange in the Multiverse of Madness on May 7, 2021, Spider-Man 3 on July 16, 2021, What If…? in Summer 2021, Hawkeye in Fall 2021, Thor: Love and Thunder on November 5, 2021, and Black Panther 2 on May 6, 2022. Marvel Studios has yet to set release dates for its theatrical releases in Ant-Man 3 and Blade or the Disney+ shows consisting of Ms. Marvel, Moon Knight, and She-Hulk.