Australia’s two-time Oscar winner Cate Blanchett has revealed she will play villain Hela in Thor: Ragnarok, and says it’s all because of her kids.

Speaking on the stage at Comic-Con in San Diego the two-time Oscar winner told an audience of 6,500 fans at the convention on Saturday that she she got involved in the franchise through a “happy accident”.

“It’s a universe that I’ve sort of been happily dragged into by my kids,” she said.

Thor’s alter ego, Australian star Chris Hemsworth, said he became tired of the Marvel Comics superhero so he spoke to Kiwi director Taika Waititi and they agreed to give him a “mid-life crisis”.

“I’ve put up with this character five times, this is Marvel’s 167th film or something. Me personally, I got a bit bored myself and thought we’ve got to try something different,” he said.

“All of us agreed, if we are going to make a third Thor we have to really push the envelope and experiment and take it to another level.

“So that was what this film was. Cut his hair, broke his hammer, changed his clothes, changed the world.”

Thor will battle with Mark Ruffalo’s The Hulk, who was seen to speak for the first time in a trailer that was premiered for the audience.

The Hulk has spent two years not as his alter ego Bruce Banner and therefore has the vocabulary of a two-year-old, Ruffalo said.

Thor: Ragnarok will be released in October.

-AAP