At the behest of editors, Kirby eventually worked in three specific references to the regular Marvel Universe throughout his series, but only one — an appearance by agents of S.H.I.E.L.D. — actively suggested that the comic took place in the same world as Marvel’s other titles. The others featured literal references to Marvel characters that could be explained away as comments about fictional entities, allowing Kirby to have his cake and eat it, too. (Those references included students building a robotic Hulk because “every member of our team is a Hulk fan,” and another character mentioning the Fantastic Four.)

Kirby's Eternals story has its origins millions of years ago when the powerful cosmic beings the Celestials created humans, the super-powered beings The Eternals, and the more monsterous Deviants.

Certainly, the concepts of The Eternals as Kirby envisioned them sat awkwardly inside a shared universe already filled with superheroes, aliens, mutants and gods; for sure, the public being familiar with intergalactic invasions and the day being continually saved by Iron Man, Captain America or Thor makes the revelation of humanity being only one of three species of humanoids as the result of manipulation by giant space aliens less unique.

The perpetually sparring Eternals and the Deviants may be previously hidden, genetically-engineered-by-aliens versions of ourselves — with the Eternals being genetically superior, and the Deviants inferior — but what does that really mean, in a world where humanity had already evolved into mutant kind and launched a public war between the X-Men and Brotherhood of Evil Mutants?

A year after Kirby’s series ended, other creators — notably writers Roy Thomas, Mark Gruenwald and Ralph Macchio — started working Kirby’s newest mythology into the larger Marvel framework, retrofitting existing storylines to include it as well as building out new concepts and stories around it: Thanos’ mother was revealed to be an Eternal, and the various monsters of Marvel’s 1950s publications to be Deviants. The Celestials, the space aliens who had created both species, were bound into both Marvel’s existential cosmology — they were agents of Eternity, the personification of the abstract concept, because of course they were. They were also bound to the everyday events of the superheroes, with the X-Men and Avengers facing villains using Celestial technology for their own ends. Eternals joined the Avengers and fought whatever threat was present that day.

All of this just served to dilute Kirby’s original core idea of the Eternals, and make them indistinguishable from his earlier creation, the Inhumans; both became genetic offshoots of humanity, created via genetic manipulation by aliens who had superpowers and fought crime, while occasionally pausing to wonder aloud if they were really like their fellow man, or somehow different.

The Eternals, as Kirby had originally created it, was something altogether different. For one thing, it wasn’t actually centered on the Eternals as a species, or a group, despite the title. (Earlier titles for the series included both The Celestials and Return of the Gods.) Instead, the focus of the series was how humanity, the Eternals and the Deviants all interrelated and, in particular, how all three responded to the ticking time bomb element Kirby introduced in the second issue of the series: The Celestials had returned to Earth to judge whether life there deserved to continue to exist. The period of judgment was the next 50 years, it was announced, giving the three species half a century to clean up their act if possible. Everything else was gravy, albeit gravy intended to be tasty enough to keep readers returning issue after issue.

Can that story be told in a world where Thanos has already rendered judgment — and, presumably, been successfully fought back by Earth’s superheroes by the time an Eternals movie is released? Or will the Eternals, Deviants and Celestials be repurposed for other ambitions altogether? (Marvel’s new Avengers comics uses the Celestials as cannon fodder to be defeated and seemingly killed in an attempt to introduce the new villain of the piece; perhaps that will provide inspiration for their movie debut.) It remains to be seen, but if there’s one thing filmmakers should take from Kirby in working out how to translate his creations into MCU properties, it’s something simple: Think big. As big as a giant space alien, if possible.