(CNN) - Despite the super-spy's prominent appearances in seven Marvel films to date, the secrets of the Black Widow's backstory have remained in the shadows.
But, as announced during the Marvel Studios panel at Comic-Con, the secrets of the notorious red on the Avenger's ledger are poised to be revealed in her forthcoming first solo film, "Black Widow," directed by Cate Shortland ("Berlin Syndrome").
After an on-stage appearance in front of thousands of fans where they revealed footage featuring fight sequences in a decidedly bone-crushing "Bourne" style, the film's star Scarlett Johansson and other members of the cast assembled on a press line to fully declassify the dossier on the Widow.
OK, who are we kidding? In a style both appropriate for Marvel's fabled secrecy and for espionage agent protocol, reporters were granted only a few choice hints as to the characters and storylines from the film.
Thirty days into shooting the movie (which has been said to take place shortly after the 2016 movie "Captain America: Civil War"), Johansson told CNN that she was still being surprised by the revelations about Natasha Romanoff, and she expected audiences to share her astonishment.
"I think you'll learn about what Natasha is afraid of, and I think you'll learn about what parts of herself she's afraid of," said Johansson. "You really see her in, like, a pretty broken-down place, and she kinda has to build herself back up and pull all the pieces together in this film. It gets kind of gnarly, but good gnarly."
Although she's has a decade of experience staying in super-heroic condition for Marvel-level action sequences, the actress admits her first solo film has physically pushed her further than ever. "Because I'm older now," she laughed. "So everything hurts. It's harder!" Even her longtime stuntwomen are acknowledging some aches and pains. "They hurt, too."
"There's three really beautifully written complicated female narratives, which is very unusual in a superhero movie -- although I guess Black Widow doesn't have superpowers: she's human, isn't she?" offered Rachel Weisz. "I can't really tell you very much -- it's all very secret -- but Melina, my character, she's been cycled through the Red Room, the Black Widow training project, the same place that (Natasha) was, trained five times since I was a child. And I'm also very involved in some scientific research -- that's all I can say."
Black Widow's Red Room origins have previously been hinted at in other notable Marvel films, most notably in flashback in "Avengers: Age of Ultron." If the screen version ultimately parallels the established comic book continuity, that indicates that young Natasha was subjected to an immersive, brutal training regimen from a very young age, along with a steady stream of female recruits being groomed to become deadly Russian government operatives and assassins.
"I've never played at anyone who's been trained as a spy," said Weisz. "I don't believe I've ever played a spy." It was suggested she's kept company with some people who excel at it, like her husband Daniel Craig. "Now and again I've come across them, yeah."
The third of the film's powerful female triumvirate is Yelena, a younger Red Room trainee played by rising star Florence Pugh ("Midsomer") who in the comics would go on to claim -- and frequently abuse -- the Black Widow identity.
"It's about these amazing, broken, powerful women," said Pugh. "They are equal, they are compatible, (they're) all hurting. I've never played anything like this before. Someone that is powerful and strong, but is dealing with things. And it's exciting to be welcomed into this world and this family alongside Scarlett in a story that I know so many people who have been wanting to here for so long."
"Stranger Things" stalwart David Harbour reveled in the opportunity to portray "Black Widow's" Alexi, who he says is the flip side of his TV role. "He's very Russian in a way that Hopper's very American," said Harbour, who hinted that his character was likely a Marvel Cinematic Universe interpretation of the comics' Alexi Shostakov, aka The Red Guardian: "He's a super-soldier, he is Russian, and he's a counterpart to Captain America."
In the comics, he's also the ex-husband of Natasha Romanoff, and has his own Russian equivalent of Cap's patriotic garb. Will Harbour don a costume as well?
"I hope that I do, but I don't know," he said with a smile. "We'll have to see."
That's all under the seal of Marvel secrecy, the lengths of which came as a surprise to "The Handmaid's Tale" actor O.T. Fagbenle, who in "Black Widow" plays Mason, Natasha's former "fixer" who still carries a torch for her.
"One day I was filming," he recalled. "You get a couple of the pages of the script that you're going to be filming that day, and at the end of the day, shooting, I like threw it in a bin. And the security guy was like, 'You cannot throw those things in the bin. They have to be shredded.' I was like, 'Oops! OK.'"