San Diego - The Avengers sequel will pit the all-star team of superheroes against Ultron.
Avengers: Age of Ultron is set for release in 2015 and will see heroes including Iron Man, Captain America and Thor team up against the mighty Ulton.
The supervillain is a self-aware adamantium robot, who has built and rebuilt himself in many different guises and incarnations and is said to be powerful enough to take over the world.
Director Joss Whedon introduced the new plans in a short video at Comic Con in San Diego. He also explained how the story will show the origin of Ultron, but not in the way most comic book fans know, with the robot originally being designed by scientist Hank Pym.
'It's a little bit darker'
He told Movieweb.com: "We're doing our own version of the origin story for Ultron. In the origin story, there was Hank Pym, so a lot of people assumed that he will be in the mix. He's not. We're basically taking the things from the comics for the movies that we need and can use. A lot of stuff has to fall by the wayside."
Joss also hinted at the idea Ultron could be created by Tony Stark/Iron Man.
He said: "We're crafting our own version of it where his origin comes more directly from The Avengers we already know about.
"It's a little bit darker than the [first] film because Ultron is in the house. There's a science fiction theme that wasn't there in the other one. Nothing can be translated exactly as it was from the comics, particularly Ultron."