Since The Flash incorporated multiverse theory into Arrowverse, pondering questions revolving around “what if scenarios” has become an integral component of what makes these series conceptually brilliant.

As we saw last year, with Supergirl transferring from CBS to the CW, the Arrowverse expanded two four shows. Consequently, the now annual multi-series crossover sees characters from Arrow, The Flash, Legends of Tomorrow and Supergirl play a pivotal role in a storyline too big for any one show on its own.

Exemplifying this point is Invasion. Invasion, last year’s multi-series event, was the first storyline to feature the last daughter of Krypton. The coming crossover event, rumoured just as complex as Invasion, revolves around Earth-X.

“We conceived this year’s crossover,” said executive producer Marc Guggenheim, “to be evocative of the annual Justice League/Justice Society crossovers we grew up with and looked forward to as kids.”

Earth-X, for individuals not familiar with this corner of the DC Comic universe, is a parallel world where Germany won the Second World War. The Amazon Prime series The Man in the High Castle addresses a reality where Nazi Germany and Japan won the war. The concept is not all that dissimilar. The only real difference is the presence of superheroes and supervillains.

While we find Earth-X is the home of former Quality Comics heroes such as Plastic Man and the Freedom Fighters (Uncle Sam, Phantom Lady, The Ray, Doll Man, et al), there are villainous doppelgangers various superheroes we know well.

“Phil was the perfect choice to bring the comic book cover iteration of this idea to life, executive producer Andrew Kreisberg said. “You can count on one hand the number of artists who could compellingly represent so many characters in a single image. Phil is one of them. And his design invokes the cover of Justice League #207, which was the 20th annual JLA/JSA crossover. Our 10-year-old selves are in heaven.”

As shown on the poster for the coming crossover, The Ray makes the leap from animated character to live-action. The Ray is the title character on the CW Seed animated series Freedom Fighters: The Ray. Similarly, Legends of Tomorrow hero Vixen has her own CW Seed animated series.

As implicated by the presence of the SS symbol on the Reverse-Flash’s chest plate, The Flash’s nemesis is just as formidable in the universe plant Earth-X exits in than he is in our own reality.

This year’s multi-series crossover will air across two nights, beginning Monday, Nov. 27, with Supergirl and Arrow, and concluding Tuesday, Nov. 28, with The Flash and Legends of Tomorrow.