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 DC Comics 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.