Eternals' post-credits scene secretly sets up the origin and history of vampires within the Marvel Cinematic Universe. With a massive cast, Eternals rightly focused on its stars—the group of ancient aliens who had been sent to Earth to protect humanity from the Deviants some 7,000 years ago. For all that's the case, though, Eternals was also in part about the MCU debut of the Black Knight, played by Game of Thrones star Kit Harington. In the comics, Dane Whitman isn't just Sersi's human lover, he's also part of a lineage that stretches all the way back to the days of Camelot and King Arthur, inheritor of the cursed Ebony Blade.

The Ebony Blade is explicitly name-dropped in Eternals, and then finally appeared in the movie's highly discussed post-credits scene. Presumably Dane has followed Sersi's suggestion of reconciling with his uncle, and has learned the truth about his family history. Consequently, in the post-credits scene Dane comes into possession of the Ebony Blade, which he believes he can use to save his beloved Sersi. The box containing the Ebony Blade contains a sinister and as-of-yet unexplained inscription reading, "Death is my reward," potentially foreshadowing the sword's blood curse in the comics. But before Dane can take up the Ebony Blade, he is interrupted by a voice from behind him—the voice of Mahershala Ali, cameoing as the MCU's new Blade.

Related: Eternals: Every MCU Easter Egg & Reference

Although Marvel considered using other heroes for this scene—one draft featured Sam Wilson's Captain America—they didn't just choose a Blade cameo at random. Speaking on a recent podcast, Eternals producer Nate Moore explained there's a connection between the MCU's Black Knight, Blade, and vampires. "The Ebony Blade, the characteristics of the Ebony Blade are not dissimilar to some degree of vampirism," he explained, "and we think that's an interesting kind of thing to play with. So we kind of knew that was on the table." The implication is that, in the MCU, there is an explicit link between the weapon—with its curse, lust to consume blood and souls, and even the fact a Black Knight cannot be killed so long as he holds it in his hands—and the history and origin of vampires.

The Black Knight points his sword towards someone in Marvel Comics.

The precise nature of this connection is still a mystery, but it's actually possible the MCU has switched things up so the Black Knight is responsible for the origin of vampires in the first place. Marvel Comics recently retconned it so Black Knight's Ebony Blade consumes the souls of those it kills, an idea that's almost Biblical in that the Word of God is described as a sword that can separate flesh from spirit. If that's the case, the first vampire could have been someone struck with the Ebony Blade, their soul stripped from their body, with a demon entering to possess them instead. The idea is certainly different to the comics, where the vampire race was created by the dark magic of Chthon contained within the Darkhold, but it can't be ruled out because Marvel Studios has never perfectly mirrored the comics.

An alternate possibility, however, is that the Black Knight is himself a vampire hunter—that the Ebony Blade is one of the few enchanted weapons capable of slaying a vampire with ease. If that's the case, the Blade cameo could mean he's kept an eye on the Ebony Blade because he saw the potential for an ally should it ever be wielded by a member of Dane Whitman's family again. This would fit with theories Marvel is setting up the Midnight Sons, a mystical team of superhero who fight against the forces of supernatural darkness. Certainly several other prospective members have been or are being introduced in Phase 4, with Moon Knight soon to step out of the shadows and persistent rumors Marvel is once again interested in Ghost Rider. Whatever the case may be, though, it's clear the connection between Black Knight and vampires will be explored after Eternals, and that it will link the history of these two mystical concepts.

More: All 12 Marvel Movies Releasing After Eternals (& When)

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