After what feels like decades of anticipation, Zack Snyder's Justice League is coming out next week. To get a refresher before seeing the film, there are two choices. First, you can read years of DC Comics, then rewatch Man of Steel, Batman v Superman: Dawn of Justice, Suicide Squad, and Wonder Woman... or you could just read this.
Going into Justice League, the main thing you need to know about Superman is that he's dead. Well, as "dead" as any major superhero can be in a comic book or comic book movie, after sacrificing himself to destroy Lex Luthor's sinister creation, Doomsday, at the end of Batman v Superman. Prior to his demise, many people believed Superman to be bad, someone who caused more death than saved people. However, his death has united people behind him, and he's become a symbol of hope as we go into Justice League. He also left behind a would-be fiancé, Daily Planet reporter Lois Lane, and an adopted mother, Martha Kent, who has moved out of the Kent family farm after Clark's death by the time Justice League begins.
We've known ever since Batman v Superman that Superman's arc in this movie would be a loose adaptation of the latter half of one of the most iconic DC comic stories: the early '90s classic Death and Return of Superman. (Specifically, the return part.) There have been lots of rumours about just which elements of the story will be borrowed from the comics in Justice League, mainly revolving around the black-and-silver incarnation of the Superman suit Clark wears when he's resurrected, right down to Henry Cavill himself trolling fans with teases. Will that be happening? We don't know. What's likely not coming? The incredibly '90s mullet Supes had when he returned in that storyline.
After teaming up with Superman and Wonder Woman to defeat Doomsday, Batman was left with a feeling that something worse was coming. Luthor warned him that Superman's death could bring even bigger threats, so Batman revealed to Diana Prince, a.k.a. Wonder Woman, that he wanted to get help from several powerful beings Luthor knew about and was keeping tabs on. The trailers have made it seem like Bruce is crucial to recruiting Aquaman and the Flash to the cause.
It's worth noting that his backstory is still tantalizingly vague, although we know it includes over 20 years of crime fighting in Gotham. That time included showdowns with the Joker (which we learned in Batman v Superman), Deadshot (which we learned in Suicide Squad), and the Penguin (a line in the Justice League trailers has Bruce and Alfred reminiscing over wind-up exploding penguins), at the very least.
Thanks to her solo movie, we now know that Diana Prince left her hidden home, the Amazon island of Themyscira, during World War I to defeat Ares, the evil God of War. After the death of Steve Trevor, she chose to exile herself in plain sight, moonlighting at a museum in Paris... although Wonder Woman actress Gal Gadot has said that part of Diana's backstory was tweaked to make way for Wonder Woman and now Justice League.
As far as we know, the only time she has revealed her true abilities since World War I was when Lex Luthor created Doomsday, although we assume other instances will be depicted, in, say, Wonder Woman 2. Until Batman v Superman, the only person who for sure knew she existed was Luthor, who owned a copy of a photograph she took after a battle almost 100 years before. Although Diana can't return to her home, some of her fellow Amazons will appear in the film in flashback sequences (we know they're flashbacks because Robin Wright's Antiope, who perished in the first act of Wonder Woman, returned for Justice League). Those flashbacks, glimpsed in the trailers, see armies of Amazons doing battle with the alien forces of the film's big bad, Steppenwolf. More on him in a bit.
In terms of the DC movies, very little is known about Arthur Curry, a.k.a. Aquaman. We know that Lex Luthor has files on four metahumans and that he is one of the four, and that Bruce Wayne stole the files and sent them to Diana Prince in Batman v Superman. The file on Curry showed that he can breathe under water and swim super-duper fast. But aside from those, his most famous ability (which may or may not be in Justice League) is that he can communicate with and command animals of the sea to do his bidding. Also, for the last time, his weapon of choice in this film is technically a quindent, not a trident.
Aquaman isn't the only Atlantean appearing in Justice League. Social media photos from director Zack Snyder have hinted that Julian Lewis Jones will make an appearance as the King of Atlantis, and we've also seen that Amber Heard is in the movie as Aquaman's future Queen, Mera. We don't know how much Atlantis will be in this movie, but you can expect to see at least Mera again as part of the Aquaman solo movie.
Like Aquaman, very little is known about Barry Allen in the context of the DC movies. He'll eventually be named the Flash, even if he isn't called that in Justice League. He's one of the metahumans that Luthor knows about, thanks to a video tape of him thwarting a robbery at a convenience store. We also know that at some point, he helped apprehend Captain Boomerang, one of the villains that's part of the Suicide Squad. These are very much the early days for Barry's career -- even if he's already designed his own fancy supersuit -- and he tells Batman several times that he's never "done battle" before and is a bit of a reluctant superhero.
Plus, though it may or may not be of consequence in Justice League, one crucial thing to know about Barry is he can travel through time... or, rather, he will be able to eventually. In Batman v Superman he appears to Bruce Wayne in a vision, ominously telling him to "find us," that Lois Lane is the key, and that Bruce is right about "him," though we don't know who "him" is. Based on the dumbfounded look on Bruce's face, the Flash believes that he appeared "too soon," which suggests whatever info he's delivering isn't wholly pertinent yet.
That will probably matter more in the planned solo film for the Flash, which was revealed to be based on the infamous alt-timeline comic story Flashpoint at San Diego Comic-Con this year. That story in the comics reset DC continuity and established the then-controversial "New 52" era of DC Comics. Whether or not the same will happen in the movies remains to be seen, but you'll likely see those time-travel powers in the Flash's standalone film rather than in Justice League.
The fourth person revealed through Lex Luthor's metahuman files is Victor Stone, a.k.a. Cyborg. Going into Justice League all you need to know about him is that a man named Dr. Silas Stone was trying to bring his dead son, Victor, a one time college football superstar, back to life. He failed. That is, until a strange device called a Mother Box, in the possession of his company S.T.A.R. Labs, somehow fused itself with Victor, creating a being that became the cybernetic superhero known as Cyborg.
Cyborg is one of the biggest mysteries of Justice League, but we have had hints that it's mainly up to Diana to convince him to join the League during the movie. It's likely that his connection to the Mother Boxes is the reason why we know so little about him yet, but we'll get to those shortly.
The Monday after the release of Batman v Superman, Warner Bros. released a deleted scene online. Called "Communion" and viewable above, it shows Lex Luthor in the bowels of the Kryptonian ship that crash landed in Metropolis. There he sees a vision of a giant being and three boxes. That being is Steppenwolf, the big bad of Justice League, and those boxes are Mother Boxes.
Steppenwolf is an incredibly powerful alien from DC's vast cosmic pantheon of beings known as the New Gods, a roster of otherworldly heroes and villains created by comic book legend Jack Kirby. He's primarily known for being a lieutenant of the iconic New Gods villain Darkseid, the ruler of the hellish planet Apokolips. Many fans expected Darkseid to be the villain of Justice League before Steppenwolf's involvement was confirmed, but there have been hints he's somewhere out there in the DC movie universe -- Darkseid's symbol, a giant Omega, was scorched in the Earth in a dream Batman has in Batman v Superman. Suffice to say, Justice League will probably deal with setting up Darkseid's inevitable arrival.
As mentioned above, at one point in Batman v Superman, Bruce Wayne has a nightmare about a world where Superman is in control. In that dream, the symbol of Darkseid is burned in the Earth and Superman somehow commands an army of giant, bug-like creatures. Those are Parademons and though they don't fight for Superman in reality, they do fight for Darkseid; they're elite alien shocktroopers that form the vanguard of Apokolips' army. Given Steppenwolf's involvement in the film, it makes sense that they will be the bulk of the villainous forces in the movie.
In the comics, Mother Boxes are wildly powerful pieces of New Gods technology -- they're like the New Gods equivalent of a smartphone, but infinitely more advanced. Fuelled by a mysterious cosmic energy called the Source, they can open teleportation portals called Boom Tubes, create force fields, manipulate the environment, and many other things. In the movies, we know they can also be bonded to people, like Victor Stone, who is resurrected and turned into Cyborg upon contact with one.
Mother Boxes form a crucial part of Justice League's backstory. The whole reason Lex was communing with Steppenwolf in that Batman v Superman deleted scene was because the alien wanted access to the three Mother Boxes housed on Earth. In Justice League, we learn that eons ago the three boxes were gifted to three different factions: one was safeguarded by the Amazons of Themyscira, another by ancient humans, and another by the Kingdom of Atlantis. We know that Steppenwolf manages to steal the Motherboxes from Themyscira and Atlantis, and we know where the final one is, because it's part of Cyborg now. Much of the conflict in Justice League will likely revolve around these powerful cuboids.
When we last left Lex Luthor, he was behind bars and bald, and Batman was promising to keep an eye on him. Meanwhile, Luthor warned that his actions in Batman v Superman had "rung a bell" to the universe -- that something in the cosmos now knows about Earth and that "he is coming." Is "he" Steppenwolf? Darkseid? Something else? We don't really know, but it was probably Steppenwolf, given he's now the villain of Justice League.
We also don't even know if Lex will actually appear in Justice League, despite being the architect of it all during Batman v Superman. Rumours have varied over the months -- at one point he was in the film and then cut, and then he was rumoured to have been restored. Even if he is in the film, it will likely be in a minor capacity rather than as a primary antagonist. But either way, he knows about these plans, so he's definitely out there someewhere.