Wanda Maximoff/Scarlet Witch – Elizabeth Olsen

While it is written in the comics that they are Magneto's children, this film mentions early on that the Maximoff twins' parents were killed when they were young, explaining their anger towards the Avengers and Tony Stark in particular. (It was his weapons that were used to bomb their fictional Eastern European town resulting in the death of their family).

She's an incredibly powerful character who uses hexes to control the people and matter around her, often using her powers to manipulate minds and break her enemies mentally rather than causing them physical harm. She is also telepathic and can receive messages from the past, present and future.

Olsen is rumoured to be reprising her role as Scarlet Witch in Captain America: Civil War later this year.

Pietro Maximoff/Quicksilver – Aaron Taylor-Johnson

We saw Quicksilver portrayed by Evan Peters (American Horror Story) in X-Men: Days of Future Past only last year but Taylor-Johnson's version is very different from the one we were presented with then. While X-Men's Maximoff was blasé, American and hard to discipline, AOU's Pietro is much more serious and burdened by sorrow and rage.

The twins are mutants, born with their abilities rather than finding them in later life or using high-tech equipment to give them power like many other characters in the Avengers universe.

Quicksilver's main ability is superhuman speed but also possesses heightened strength and keen fighting skills when in combat. He is dedicated to protecting his sister as she is the only family he has left and the two are strongly reliant on each other.

Avengers: Age of Ultron
Andy Serkis as villain Ulysses Klaue Marvel

Ulysses Klaue – Andy Serkis

Serkis lands himself a small, yet great cameo in Age of Ultron as Klaw, a supervillain stemmed from the comics who is an antagonist for not only the Avengers, but later on the Fantastic Four and Black Panther too. Look out for the claw necklace he wears around his neck, it's most definitely a nod to his foe Black Panther with whom he shares many comic book storylines.

In Age of Ultron, he is first and foremost a black market dealer who steals and sells weapons from his base in South Africa. Back when Iron Man/Stark used to be involved in weaponry, the pair were acquainted.

Dr Helen Cho – Claudia Kim

A similar support character to Thor's Erik Selvig (played by Stellan Skarsgård), Helen Cho is a geneticist and an ally of the Avengers who works in the research department Bruce Banner's laboratory in Avengers Tower, New York.

Within the movie, she is mind-controlled by antagonist Ultron using Loki's sceptre so he can use her incredibly smart brain and knowledge of technology when creating his own android partner to take on the Avengers.

Avengers Age of Ultron
James Spader's Ultron in his maniacal, menacing glory. Marvel Studios

Ultron – James Spader

The Blacklist star James Spader lends only his voice to the second movie, bringing to life Ultron, a malevolent artificial intelligence so hell-bent on saving the Earth that he arrives at the conclusion that it will be better off without the human race altogether, leaving just a world of robots like himself behind.

Initially brought to life by Tony Stark as a prototype for an AI army that he believes could protect the world against other-worldly threats that they struggle maintain, Ultron grows sentient during his creation and impulsively breaks free from his master's control to destroy the Avengers and obliterate everyone who stands in the way of his mission.

In the press conference for the movie (21 April), director Joss Whedon highlighted just how early on they decided on the villain for Age of Ultron, stating: "I said we should have Ultron on the second movie before I even decided to make the first one. He's big, he's powerful, he's angry and he's metal. He's strong enough to take these guys on. He's been so angry for so long, I think he might be a little unhinged and I can write that."

Vision – Paul Bettany

Paul Bettany has actually been a part of the Marvel Cinematic Universe since the first Iron Man (2008) but due to the nature of his role, audiences will have never seen him on screen. Up until now Bettany has voiced J.A.R.V.I.S, a highly intelligent computer program created by Tony Stark, in five movies.

Now, the Da Vinci Code actor steps out from behind the recording studio microphone in Age of Ultron to embody Vision, an android which is able to think through the power of an Infinity Stone. Created by Ultron to be his accomplice but then reprogrammed by Stark and Banner to be just the opposite, Vision's true loyalties are questionable causing the Avengers to be cautious when trusting him to help them defeat Ultron.

He has the ability to change his density, giving him the possibility to become super-strong when he raises it and be able to levitate when it is lowered. He can lower his density so far that he can even pass through solid objects and appear as if he has disappeared. He can also cast intense energy beams from himself.