In Marvel Studios' fourth Thor movie, Thor: Love and Thunder, Natalie Portman will return to reprise the role of Jane Foster, Thor's human love interest who has been a relatively minor player in the Marvel Cinematic Universe. However, Portman's character won't just be an astrophysicist in the upcoming film. Following in the footsteps of her comic book counterpart, she'll also wield Mjolnir as the Mighty Thor.
Even though that film isn't set to be released until 2021, one of the key aspects of her transformation may be an Infinity Stone that's already in the MCU.
In 2013's Thor: The Dark World, Thor has returned home to Asgard following the events of The Avengers to find the Nine Realms in chaos. Meanwhile, Jane alongside her intern Darcy investigate a disturbance in an abandoned warehouse in London where they find a portal back on Earth. Jane elects to enter the anomaly and transports to another world where she comes into contact with a fluid, ever-changing substance. After absorbing the Aether makes her fall ill, Thor takes her to Asgard for treatment.
Odin quickly identifies the infection as the Aether, the Reality Stone, which his father Bor fought to keep out of the hands of the Dark Elf Malakeith. The Infinity Stone grants its user the ability to alter reality on a massive scale, as was seen when Thanos acquired the stone from the Collector in Avengers: Infinity War.
Like the other Infinity Stones, the Aether will kill anyone who touches it if they're not powerful enough to wield it. So, Thor, Loki, and Jane travel to the Dark Elf homeworld in an attempt to extract the stone from Jane and destroy it from good. While successful with the former, Thor is unable to destroy the Aether, but eventually puts an end to Malakeith's plan later in the film.
While Thanos eventually acquired the Aether to assemble the Infinity Gauntlet, there's no guarantee that Jane's lengthy time with the Aether wouldn't have had left some of its residual powers in her.
If she even has a fraction of its reality-bending power, she could theoretically create or wield Mjolnir. Jane's connection with the Aether puts her into some uncharted waters as she's one of the only characters in the MCU to wield an Infinity Stone as long as she did. What's to say she didn't absorb some residual energy from that stone that allows her to alter reality.
In Jason Aaron's Mighty Thor run, which Thor: Love and Thunder is drawing inspiration from, Jane is diagnosed with cancer around the same time that Thor loses his ability to wield Mjolnir. Soon after, a mystery woman gains power of the hammer and begins facing evil using the mantle of the God of Thunder. It's later revealed that the woman is Jane who wields Mjolnir while fighting her ailment. However, Jane's use of the hammer perpetuated her cancer as a result of the transformation purging all toxins from her body, including the chemotherapy being used for her treatment each time she transforms.
With the Aether, the MCU's Jane could find herself in a similar set of circumstances. We've already seen the Aether harm her, and her using it to wield Mjolnir could be quite detrimental to her health. It could also be a way to give Portman's Thor a tragic, compelling arc inspired by the comics.
Directed by Taika Waititi, Thor: Love and Thunder starring Natalie Portman, Tessa Thompson, and Chris Hemsworth arrives in theaters November 5, 2021.