Please be aware this post contains spoilers for Wonder Woman.
Most superheroes have a signature weapon or two. Cap's got his shield, Daredevil's got his billy club, and Wonder Woman's pretty much got an arsenal of trademark tools. Now that the iconic comic book character finally has a film of her own, she's got a new weapon: the God Killer. Well, kind of. Wonder Woman first introduces the God Killer as a legendary sword, a familiar incarnation for fans of the comics, but the sword itself is ultimately revealed to be nothing but a tricksy McGuffin that leads Diana (Gal Gadot) to the realization that she is the God Killer, which means she's also a goddess. Talk about a journey of self-discovery. Ultimately, it's that journey that cements her journey from a wide-eyed and fearless moral champion to a battle-hardened hero by choice.
It was a bit of a surprise when we first learned that the God Killer was going to turn up Wonder Woman at all. The weapon is a recent addition to the DC Comics universe, and it hails not from Wonder Woman but from Deathstroke. Plus, as I mentioned, Wonder Woman's got a veritable arsenal of her own canonical weaponry between the Lasso of Truth, the Sandals of Hermes, the Sword of Athena, the invisible jet, the bracelets, the shield, and even the tiara. Why the God Killer then? Most likely, it's a simply a means of diversion to keep the audience off-balance until the Wonder Woman's big third-act reveals. It's a familiar and powerful enough weapon to keep people guessing, but not one so vital it can't be reimagined for the cinematic universe. Of course, Deathstroke is set to join the DCEU soon, so it's possible if not likely that the misdirect is also setting the stage for the appearance of the actual God Killer sword. (Ares tells Diana only a god can kill another god, so probably not, but most people in this movie except Diana are a big ol' liar, so who knows.)
As for its comic book origins, the God Killer was introduced in the 2015 issue Deathstroke #7, in which Slade Wilson is recruited by the Greek god Hephaestus to kill the Titan Lapetus. Hephaestus arms the assassin with a superpowered sword that will allow him to defeat immortals and what an extraordinary set of powers the God Killer has. It can guide and strengthen the wielder, compelling them to action, it can unleash shock blasts, it can shape-shift mid-battle into superior forms of weaponry, and it even has some whacky psychic powers, drawing out and feeding on the memories of opponents. It's a fearsome and many-faceted weapon, forged by a god, that makes a super soldier like Slade Wilson capable of kicking Superman's ass. If you're wondering, though Wonder Woman doesn't wield the God Killer in the comics, she does play a significant role in the God Killer comic book arc. Wilson's journey brings him to Themyscira and Tartarus, where he trades blows with Wonder Woman before eventually teaming up with the Amazon to track down and destroy Lapetus.
In the film, it's rather a different story. For one thing, the sword can't do any of that crazy stuff. It's just a sword that, legend has it, can kill immortals. The God Killer is still tied in with Greek mythology, but the purpose is different. In Wonder Woman, Hippolyta tells us that "when time was new and all of history was just a dream", Zeus created mankind, beings that were righteous and good. Ares, the God of War, grew envious of his father's new creation and "poisoned their hearts with jealousy and suspicion," encouraging them to tear each other apart with war. That's when Zeus created the Amazons to influence men's hearts with love and restore peace on earth. It worked, but only for a time, and Ares waged a war against the gods, killing them one by one, and ultimately dethroning his father. Queen Hippolyta (Connie Nielsen) and her sister General Antiope (Robin Wright) led an insurrection that won the Amazons their freedom, but Zeus was defeated and with his dying breath, he created the God Killer and the island of Themyscira, where the Amazons could protect it and keep it hidden from Ares.
Growing up on Themyscira, Diana is told the legend over and over again from her mother, Queen Hippolyta, who tried to protect her daughter from her destiny by keeping her from the battlefield and traditional Amazon training, despite Diana's protestations. Fortunately, the unfathomably badass Aunt Antiope is there to defy her sister's wishes, training Dianna on the sly to become a great warrior and fulfill her duty as the God Killer. (Even if no one has the sense to tell her about her true identity. That information would have been pretty useful, guys.) So when Steve Trevor (Chris Pine) crash lands on Themyscira's shores, bringing a deadly hail of German gunfire with him, Diana learns about The War to End All Wars and believes that it is her duty as an Amazon to defeat Ares and bringing mankind to peace once again. So she snatches up the God Killer from its golden cradle, jailbreaks Steve Trevor, and sets out to the world of men after a tearful last-minute goodbye with her mother (who still does not tell her about her true identity).
Wonder Woman is not only Diana's origin story, it's her coming of age film. We see the guileless, pure-hearted young demigoddess make bullheaded mistakes and foolish acts of innocence on her way to maturity. The big one, of course, is her intertwined insistence on charging into battle with Ares and refusal to believe in the darkness of mankind. When Sir Patrick (David Thewlis) reveals his true identity to her, he also gives her the opportunity to discover hers. Dianna believes it is her duty to defeat Ares, but she's still woefully clueless about who and what she actually is, and that is the ultimate payoff when she discovers that she was always the God Killer and the sword is nothing but metal, disintegrating like the illusions of youth at Ares' touch.
In that moment, we watch Diana, the morally righteous Princess of Themyscira become Wonder Woman, with all her power and autonomy unleashed. Without her naive convictions to drive her, at her moment of greatest grief, and with the power of a god at her fingertips, Diana still chooses to do what's right and in that moment she becomes the hero she was destined to be. She also becomes exactly the hero we need right now. We've seen a Bruce Wayne broken by the times, we've seen a Superman taught to fear mankind's wrath and xenophobia -- those interpretations aren't inaccurate, the world is dark as hell right now, which is exactly why we need a hero like Wonder Woman, who stares right in the face of that darkness and injustice at her worst moment and still chooses to do the right thing.
