The second film takes place one year after the events of The Avengers and two years on from the first Thor film. It follows Thor (played by Australian actor Chris Hemsworth) as he reunites with Jane to save the Nine Realms from an enemy older than the universe.
Emmy-winning Sopranos and Game of Thrones director Alan Taylor takes over from the first film's director Kenneth Branagh. Coming from the dark world of Game of Thrones, Taylor says he found the first movie a little too "shiny".
"There was a deliberate attempt by me to darken this film," says Taylor. "Thor was a young prince in the first one. He has grown up a bit and things get more complicated and sacrifices get bigger, so it's a darker story we're telling.
"I love the first movie and the cast and everything Ken Branagh did, but the thing I had issues with was that the world was too shiny for me. I thought coming into this world, it should feel ancient. Yes, he's a superhero, but he's also the only superhero who's God-like and who has thousands of years of Norse mythology on top of that, so I wanted to make sure it was rooted in the mythology."
Taylor still finds it "surreal" to witness the intense fan following Marvel films has attracted at conventions like Comic-Con and Disney event D23.
While many were surprised when he nabbed the director's hat, the cast were welcoming. Portman says it was an easy transition from Branagh to Taylor.
"Alan's incredible and he has such great experience with this kind of thing after Game of Thrones, so it was really natural to have him work on it. He was great at giving us an idea of what was going on around us, which is important because so often you're shooting against a blue screen, so you don't know where things are. It's up to the director to orient you and he was great at communicating that to us."
Of course it's her working relationship with the film's lead star Hemsworth which has made Portman the envy of the movie's female audience. The former Home and Away actor has quickly become a huge Hollywood star.
Portman says the pair got along so well they had trouble getting into work mode.
"Chris is awesome. He's super-fun and so professional but we definitely had a bit of a problem on this movie because we would get into giggle fits. We're too grown up and too old to be acting like that, but we had a few days where the crew at a certain point were like, 'Okay guys - enough!' because we just couldn't stop laughing."
Thor: The Dark World opens in cinemas on Thursday.
