Even before seeing Eternals, fans knew the film would set up future adventures in the cosmic pocket of the Marvel Cinematic Universe. Given they're the Celestials' lapdogs who were sent on a secret mission to Earth, it wasn't hard to predict that it'd paint an even larger galactic canvas than initially assumed, which now leaves fans wondering what's in store for the likes of Nick Fury and Captain Marvel later down the line. However, another major facet that's put into motion as Eternals ends is a dark, powerful "Anti-Thor" who could prove to be quite troublesome.
This is none other than Kit Harington's Dane Whitman, who comic lovers know as the Black Knight. He doesn't get much screen time here, other than being Sersi's present-day love interest after her romance with Ikaris fizzled out, but he does play a key role.
After Sersi and the others are kidnapped by Tiamut, in Eternals' post-credits, Dane decides to open up his family's trove, unearthing the Ebony Blade. This is the weapon that'll transform him into the Black Knight but while fans think this is Dane's first step towards becoming the hero who's helped Captain Britain and MI:13 and who'll eventually be an Avenger, recent developments position him as more of a threat.
In the recent Black Knight: Curse of the Ebony Blade miniseries, it's revealed that the Ebony Blade draws upon the darkness in the wielder's heart. So, the more impure and unworthy they are as a person, the stronger they'll be. It's why Dane becomes so powerful, with the weapon not creating evil inside, but just exacerbating what's already there.
As such, it's the opposite to Mjolnir, which can only be lifted by those worthy, whether it be Thor or Captain America. The thing is, this blade has just as much destructive power as Mjolnir, going back to Camelot's days where Knights destroyed armies by themselves. It explains why Merlin and Mordred wanted to harness its powers, why King Arthur believed in it as a weapon of mass destruction and why Knull craved its rage. Moreover, it was used to beat down Thor in medieval times, thus proving that it can best the Odinson and his hammer, which is what the spirit of Percy tried to tell Dane, his descendant, in the source material. He knows how dangerous it can be from his time as the Knight, and Dane finally starts realizing what it can do.
The Ebony Blade also resurrects its wielders if they die holding it so, in essence, it can make its evil Thor immortal. To rub salt in the wounds, when Thor tried to lift the sword in this book, he couldn't, as he didn't have the necessary darkness inside. Thus, should Dane use his grief from missing Sersi or even dive into the past to discover his sadistic dynasty and what his ancestors were -- killers -- he may go berserk, coming off like a mix of Hulk and Thor.
He did lose control in battle already with this power boost, so Dane may end up being an anti-hero in the MCU, which would explain why Blade recruits him in Eternals' post-credits scene. After all, he'll probably need folks who are willing to break rules, whether it's against vampires or other creatures of the night. Ultimately, it remains to be seen if Dane will truly become Thor's polar opposite but if he does, given how emo he is, he may well end up becoming corrupted and a liability. Or worse yet, he could become an enemy of Earth's Mightiest Heroes or even Sersi, should they ever be reunited in the ever-expanding MCU.
To see how Dane's Black Knight is set up, Eternals is streaming now on Disney+.