Production on "Justice League: Part One" is currently underway in London, and while there are still many secrets surrounding the cast and plot of the DC team-up flick, filmmakers have revealed a few key pieces of intel to whet fans' appetites.

Mashable recently visited the set, and chatted with director Zack Snyder and producers Deborah Snyder and Charles Roven. Deborah Snyder confirmed that the main villain in the film will be Steppenwolf, a mysterious figure that Mashable spied in concept art that depicted "a six-foot, shadowy silhouette with two horns sprouting from its faceless head." Producers are "close" to casting the supervillain, Snyder said, though she declined to name just who is in the running for the part.

When it comes to supporting villains, it's still unclear just who will be helping Steppenwolf antagonize the titular superheroes. Synder demurred when asked about whether Steppenwolf's nephew, Darkseid, will appear in the flick, telling Mashable, "I think you're going to have to wait to see about that." (Mashable seems to think that that coy answer all but confirms Darkseid's appearance, since the villain's presence was hinted at heavily during a dream sequence in "Batman v Superman: Dawn of Justice.")

Other notable takeaways from Mashable's report include the fact that "Justice League"'s tone is very different from that of the critically-maligned "Dawn of Justice," and that the movie will be a self-contained story, not necessarily a cliffhanger-ending film meant to lead directly into "Part Two." The mysterious Motherboxes will also feature heavily into the plot, while Superman (Henry Cavill) may not show up until partway into the flick. And fans should expect Ben Affleck's Bruce Wayne/Batman to face some resistance when it comes to forming the Justice League, especially from Aquaman (Jason Momoa).

"It's about trying to get a lot of disparate people who are used to being very powerful and very independent to try to work together, and it's about how hard that is," Affleck explained to Mashable. "There are some characters that really hit it off with each other, some that really don't hit if off with each other and almost come to blows, and it's about trying to contain that."

Read the entire report here. "Justice League: Part One" opens on November 17, 2017.

[via: Mashable]