Jake Gyllenhaal, who once almost replaced Tobey Maguire in director Sam Raimi's Spider-Man 2, is now going to face off against Tom Holland's friendly neighborhood wall-crawler.

The Brokeback Mountain star will join the Sony side of Marvel's Cinematic Universe as the villain Mysterio. He'll appear in the upcoming sequel to 2016's Spider-Man: Homecoming.

Gyllenhaal all but confirmed the news in a post on his shiny new Instagram account on Wednesday:

The Instagram video features Gyllenhaal reading an old issue of The Amazing Spider-Man, with a glaring cover that announces "The Return of the Man Called MYSTERIO!"

This will be Gyllenhaal's first real comic book movie. He's no stranger to big-budget blockbusters (The Day After Tomorrow) or geek-friendly adaptations (Prince of Persia: The Sands of Time), but Spider-Man 2 was the closest he ever came to participating in a big screen superhero story.

Precious little is known about the Homecoming sequel, probably due in large part to the cliffhanger ending in Avengers: Infinity War. There's a big, unresolved story unfolding right now in the MCU and it's not going to wrap up until Avengers 4 arrives in 2019.

That said, Mysterio is an unusual figure in Spider-Man lore. The fact that he's involved at all raises a bunch of questions.

The most well-known version of the villain is the original. Special effects master and stuntman Quentin Beck had dreams of Hollywood stardom that never panned out, so he turned his attention (and his considerable skill at creating illusions) toward supervillainy.

Beck doesn't possess any superhuman abilities. He relies instead on his expertise in the Hollywood technical arts coupled, a natural knack for hypnotism and spinning illusions, and a background in robotics and chemistry both.

He's a villain who relies more on brainpower than superpower. Beck frequently employs holograms and a hallucinogenic gas of his own design to create more of an even playing field when he squares off against superheroes.

His costume memorably features a fishbowl-shaped helmet that swirls with gas, concealing his face. In those situations, Beck relies primarily on built-in sonar to "see" his way around. While the movie version will likely take some liberties, Mysterio's iconic (and goofy-looking) helmet probably won't be going anywhere.

Confirmation of Mysterio's involvement in the Homecoming sequel does open up another possibility, however. Long ago, before Sony and Marvel joined forces, a Sinister Six project was announced. That project's status is unknown now, but it may still be in the cards.

Sinister Six is a supervillain team that has frequently clashed with Spider-Man in the comics. Mysterio was one of its founding members, as was Michael Keaton's Homecoming villain, Vulture. And notably, Homecoming's post-credits scene featured an imprisoned Mac Gargan — the human behind Spidey supervillain, Scorpion — hinting at friends on the outside who have a bone to pick with Spider-Man.

All of this is pure speculation for now. But we know Sinister Six has been in Sony's movie plans before, and Mysterio's arrival in the Homecoming corner of the MCU lays additional groundwork, on top of what's already, for making it happen.