Following the completion of its first season on CBS, it was announced that Supergirl was renewed for season 2, but it would move over to The CW, a network co-owned by CBS and Warner Bros. As a result, Supergirl will kick off the Fall TV season alongside fellow CW superhero series Arrow, The Flash, and Legends of Tomorrow. Shortly after the announcement of the move, CW president Mark Pedowitz teased the “biggest” superhero crossover, combining heroes from all four series across a four-episode event.

Now, production has begun on the mega-crossover – which will include Arrow’s 100th episode – with fans receiving teases via Arrow star Stephen Amell’s social media feeds. Most recently, the actor posted a photo of himself suited up as the Green Arrow alongside Melissa Benoist in costume as Kara Danvers aka Supergirl. However, little was known about what fans could expect from the crossover event, and what villain the superheroes would be tasked with fighting. That is, until now.

EW is reporting that The CW superhero crossover will be loosely adapting the DC Comics comic book crossover storyline Invasion! from the 1980s, and the heroes will be facing off against the alien race known as the Dominators. Arrow and Legends of Tomorrow executive producer Marc Guggenheim explained the crossover villain:

“This year, for our mega ‘Arrowverse’ crossover, we’re taking inspiration from a DC crossover from the late 1980s known as Invasion!, which featured an alien race called the Dominators, who’d previously vexed the Legion of Superheroes. We’re using cutting edge prosthetics and computer effects to achieve a feature film-quality look which is faithful to Invasion! artist Todd McFarlane’s interpretation of the characters.”

In the three-issue Invasion! comic event, the Dominators form an Alien Alliance with the intention of invading Earth and harnessing the power of its metahumans in order to create their own army of super-powered beings. Though the Dominators and their allies pose a threat to Earth, after the Daxamites abandon the Alien Alliance to help Earth’s metahumans, the Dominators are defeated. Given these details about the plot of Invasion!, we can make sense of previous comments made by Guggenheim and Arrowverse producer Greg Berlanti.

Guggenheim originally said the crossover would include an “external threat” that would necessitate Supergirl travelling to the other three shows; certainly the Dominators qualify as an external threat and since they’re extraterrestrials as well, Kara – and Martian Manhunter (David Harewood) – may be able to provide necessary insight and aide in their defeat. However, Berlanti later revealed the main storyline of the crossover would start on The Flash, and continue to Arrow and Legends of Tomorrow while still including Supergirl.

That said, given the inclusion of Daxamites in the Invasion! storyline, it’s possible Supergirl may offer more setup for the crossover than indicated by Berlanti or Guggenheim. At the end of Supergirl season 1, a new pod crash landed on Earth, which it was later revealed will contain the Daxamite named Mon-El (Chris Wood). His arrival may act as setup for the invasion led by the Dominators. Still, the inclusion of Supergirl and the Dominators in the crossover largely depends on how The CW’s DC Comics series adapt the Invasion! storyline. So, it remains to be seen how the crossover event comes together as more information is released.

Next: The Flash-Supergirl Musical Crossover Episode Confirmed

The Flash season 3 will premiere Tuesday October 4 at 8pm on The CW, Arrow season 5 will premiere in the same timeslot on Wednesday October 5, Supergirl season 2 on Monday October 10, and Legends of Tomorrow season 2 on Thursday October 13.

Source: EW, The Flash/Twitter