It's been a while since we last saw an installment in Vin Diesel's other franchise on the big screen, but all that changes when "Riddick" opens in theaters on September 6.

In the film, Diesel reprises the role he originated in 2000's "Pitch Black." It's the first appearance of the fearless mercenary Riddick since his appearance in the decidedly more epic "Chronicles of Riddick" from 2004. But nine years away from theaters is a long time; Diesel's made three "Fast and the Furious" films starring his character Dom Toretto in that gap. What kept the ferocious Furyan out of theaters for so long?

"The trick was to service both the audience from 'Pitch Black' and the audience from 'Chronicles of Riddick,' and do that all while maintaining a rated-R feel," Diesel revealed to MTV at San Diego Comic-Con. "And as you know, when you're doing the really, really big budget movies, it's difficult to get a studio to sign off on a rated-R movie. And yet, they did -- or they finally did."

"Finally" is definitely the key word there. The modestly budgeted and R-rated "Pitch Black" was a surprise hit when it was released, finding a cult audience that craved more of the antiheroes antics, but the big-budget follow-up "Chronicles of Riddick" came up short at the box office. Diesel hypothesized that that may be due to the difference in the R-rated original and the less successful sequel's softer PG-13 rating.

"['Riddick'] is an intense film," explained Diesel. "Being a rated-R film sets it apart from the other stuff that you see, so it's not the four-quadrant Dom Toretto, take care of his family character. It is, in some ways, the antithesis of that. There's something that the audience really keyed into about it being rated R."

The film sees the franchise return to its thriller-based roots, eschewing the high-concept sci-fi that fans feel bogged down the second film. This is a development that Diesel is positive fans will enjoy.

"They were very vocal about the fact that they wanted," Diesel said. "They felt like kids get 'The Pacifier' and 'Iron Giant.' The world gets 'Triple X' and Dom Toretto. Give us our 'Riddick,' and we want it dark, and we want it morbid, and we want it all things Furyan."

From "Romeo and Juliet" to "Ender's Game," "Riddick" to "Oldboy," the MTV Movies team is delving into the hottest upcoming flicks in our 2013 Fall Movie Preview. Check back daily for exclusive clips, photos and interviews with the films' biggest stars.