The flick sees Ruby star as Ali, a former soldier who returns to New York City and takes a job as a doorman at a fancy high rise building during its renovation, only to find thieves are using the building work as a cover to locate something hidden somewhere in the hotel.
Speaking to website ThirdCoastReview.com, the star revealed she did "99.9 per cent" of her own stunts in the movie, insisting she had no idea how intense the Ryuhei Kitamura- directed movie was going to be.
"I didn't know that the stunts would be as incredible as they were," she explained. "Ryuhei specialises in that, so I did know it would be incredible, but I didn't realise until we were training quite how much he believed in me to pull off really long sequences and really crazy stuff."
According to Ruby, there was one stunt - a backflip - that she didn't do herself but, after seeing her stunt double, who she described as a "short, stocky, muscular dude," she realized she'd have to step up to the game.
"I took one look at him and said, 'That's not going to work, so I'll be doing all of this'," explained the actress. "Again, I loved that because once I realized I'd be doing all of it, I was like 'We have to get right into this.' "
She continued, "I feel very grateful for that because it is fun kicking butt for that long. But what really drew me to the film was that I really like Ryuhei as a director - he was already attached - and I love action films, I love being physical."
She went on to admit "it was the story that drew me into" the project, because Ali is an "entirely different to any character I've played before."
"I don't like playing the same character twice, and in action, sometimes there are types of characters that feel familiar, and even if it's a good script, that's great, but I've already played this character or an iteration of this character," explained the "Batwoman" star.