Dane Whitman discovers the Ebony Blade in Eternals' end-credits scene, setting up an arc that positions him as an evil mirror to the MCU's Thor. Dane (Kit Harington) has a relatively small role in Eternals, serving as a romantic interest for Sersi but not just as a character with any great powers of his own — yet. It's clear from the movie, though, that Dane has a big MCU future, which Eternals post-credits scene in particular plays a major role in.
The Eternals' after-credits scene with Dane should come to define his future in a few key ways. There is, of course, the voice of Blade (Mahershala Ali), questioning whether he's ready for the Ebony Blade and setting up a possible team-up between the pair. There's the mention of Dane's uncle, something referenced a couple of times during the movie, which further establishes his family lineage as being important. And there is the Ebony Blade itself, connected to both and yet the most crucial in its own right, which can cement Dane's future as Black Knight.
Related: Blade Wants Dane Whitman's Sword For Himself — Eternals Theory Explained
The Ebony Blade is an ancient, mythical sword, and it's with this that Dane's arc will serve as a dark mirror to Thor's. The Ebony Blade is essentially the anti-Mjolnir; where the latter seeks worthiness, the former rewards those who are most impure of heart. The Ebony Blade amplifies the worst characteristics of a person, feeding on the most evil parts of them and their most negative thoughts, which in turn allows both the blade and its user to grow stronger. It drives them further down this path, leading to a lust for violence and bloodshed. In Marvel Comics, this was the fate that befell Dane's uncle, Nathan Garrett, who held the mantle of
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