LONDON — It's no secret that many Bothans Rebels died to secure the plans for the Death Star. It's part of the Star Wars mythology. But have you ever wondered how many died? Or how the entire Rebel mission materialized? Or who led the group of Resistance fighters to victory? (Her name is Jyn Erso, and she’s here to kick some Imperial ass.) If so, then Rogue One is the Star Wars story for you.

Sure, we've heard all about their fateful mission, but we don’t exactly know how it all went down — until now. It involved explosions, Shadow Troopers, infiltrating the Imperial Army, and plenty of Forest Whitaker.

Star Wars Celebration capped off its first day in London — 40 years since A New Hope wrapped in the city — with a Rogue One panel moderated by Captain Phasma herself, Gwendoline Christie. Director Gareth Edwards and producer Kathleen Kennedy were joined by the entire cast of the film, including Star Wars's latest heroes, Felicity Jones (Jyn) and Diego Luna (Captain Cassian Andor), and its terrifying new villain, Director Krennic (Ben Mendelsohn).

Rogue One: A Star Wars Story is the first of three planned stand-alone stories in the Star Wars universe. "We have this amazing opportunity to tell stories inside this incredible universe," Kennedy said. That means introducing different characters, different planets (including a paradise planet known as Scarif), and "different experiences all around."

Executive producer John Kroll, who originally pitched the idea to Kennedy, also revealed the first piece of conceptual art for the film, which featured a ragtag group of Rebellion fighters on a very important mission.

Edwards once again reiterated that Rogue One is a darker, more immersive, more realistic look at that galaxy far, far away, and the Celebration crowd certainly got that sense of that in the sizzle reel the director premiered at the convention. The behind-the-scene clip features brand-new footage of the Rebellion squad at work — fighting the Galactic Empire, blowing up Stormtroopers, stealing top-secret information, and so on — and highlights Mendelsohn's charismatic Krennic (and his stylish white Imperial cape). But it's Jyn's remarks in the reel's closing moments that really gave everyone chills: "May the Force be with us."

Jones’s antihero Jyn is a rebel without a cause (with a gun belt "inspired by Han Solo"), and that’s exactly the kind of attitude the struggling Rebellion needs. She's ultimately tasked with a mission from Mon Mothma: Steal the Galactic Empire’s plans for their shiny new weapon of mass destruction, the Death Star. But just as Rogue One is a different kind of Star Wars film, Jyn is a different kind of hero. Unlike heroes Luke Skywalker and Rey, Jyn has had a "very full life" before we meet her in Rogue One.

"She's not a character who's asking, who am I and where have I come from? We already know that," Jones said. "And that fact is the beginning of Jyn's journey."

Jyn's relationship with her father, Galen Erso (played by Mads Mikkelsen), is the emotional crux of her story. When pressed for more information, however, Mikkelsen chose to play it safe. "As you know, there's a lot of secrecy around for good reasons," he said. "My character is a character of interest."

But he did reveal a particularly tantalizing piece of information: "He's a scientist and he at one point invented something so beautiful, so fantastic that it might change the universe." Oh.

Similarly, Mendelsohn's big bad is a different kind of Imperial villain. "He is smarter, I think, than most of the others," the actor said after making a grand entrance, dressed in Krennic's Imperial duds and flanked by a mini-army of Shadowtroopers. "He's more inventive. He's perhaps a little sexier that some of them — not as sexy as some of the others."

Of course, Jyn won't be alone in her endeavor. She'll be joined by a group of resistance fighters. Captain Cassian Andor, her right-hand man, works intelligence for the Rebellion. Luna admits that there's "friction" and "issues" among the team but that Cassian keeps them together. His best friend is a curmudgeonly Imperial droid that he's reprogrammed named K-2SO (voiced by Alan Tudyk).

Celebration-goers were treated to an exclusive (albeit silent) scene between K-2SO, Jyn, and Cassian. In it, Jyn hands K-2SO her pack, and he drops it — out of principle, of course. He's not the kind of droid who's going to carry your shit. "He's not quite all there," Tudyk said. "He speaks his mind and says things that can be unsettling. [He's] just very honest."

And yes, Tudyk has already met Anthony Daniels (C-3PO). The two met at the opening night party for The Force Awakens. "He asked, 'Do you wear a suit, or are you CGI?' and I said, 'Oh, it's CGI.' And he said, 'You shit.'"

Riz Ahmed plays a pilot named Bodhi, who, despite his Imperial jacket, is a rebel at heart. "Bodhi works for the Empire to earn a living," Ahmed said. "People work at big organizations, and they don't agree with everything they do. So he's questioning things."

Bodhi's home is Jedha, a spiritual planet that is currently being occupied by the Imperial Army at the start of Rogue One. This makes Bodhi question his allegiance. Jedha is important for several reasons. Not only is a major location in Rogue One, but it also shares the closest ties with the Jedi. Remember, Rogue One takes place at a time where there are allegedly no Jedi remaining. But that doesn't mean people have stopped believing in the Force.

In fact, Chirrut (Donnie Yen) is a spiritual warrior-monk of sorts. "I can't see, but I can feel with my heart and believe in the Force," Yen said. Chirrut is joined by his good friend Baze (Jiang Wen). According to Yen, they are two of the "baddest fighters in Jedha." However, their styles couldn't be more different. Chirrut is all heart, whereas Baze is brute force and big guns.

"Baze doesn't believe in the Force," Wen said. "He's a thinker [pointing to Yen], I'm a doer."

As for the indomitable Rebel fighter Saw Gerrera (Forest Whitaker), he's going to extremes to defeat the Empire. "He's been fighting for years against the Imperial," Whitaker said. "He's controlling a group of rebels that are out to the extreme."

Celebration also premiered a new teaser trailer — the full-length version will most likely make its way online soon — and it revealed the first official look at seminal Star Wars villain Darth Vader, who is confirmed to make an appearance in Rogue One. "Every day we grow weaker while they grow stronger," Jyn says before Vader takes a breath and his reflection is revealed.

Oh, and about those casualties... one Rogue One star who will remain nameless may have spoiled his/her grim fate. Oops?