One of the biggest questions surrounding the highly anticipated crossover between "Arrow," "The Flash," "Supergirl" and "DC's Legends of Tomorrow" has at last been answered: the identity of the big villain for the CW event.

Warner Bros. revealed this afternoon that the heroes of the "Arrowverse" will face off against the Dominators, the gene-manipulating DC Comics aliens who over the years have plagued the Legion of Super-Heroes and Justice League. They're perhaps best known for their prominent role in DC's 1988-89 crossover event "Invasion!"

"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 Super-Heroes," "Arrow" and "Legends of Tomorrow" Executive Producer Marc Guggenheim said in a statement. "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.”

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Introduced in 1967's "Adventure Comics" #361, the Dominators were initially a 30th-century foe of the Legion of Super-Heroes who had been engaged in a lengthy war with the United Planets. In "Invasion!," however, they appeared in the 20th century, where they assembled a coalition of alien races to invade Earth, with the apparent goal of eliminating the threat posed by "metahumans" -- that is, super-powered people. Unknown to the other members of the alien alliance, the Dominators intended to harness the metagene and create their own army of metahumans.

Needless to say, the invasion was thwarted, but not before a Gene Bomb designed to kill metahumans detonates, but has the unintended consequence of creating more metahumans. It's easy to see how that plot element could play into the plans for The CW's superhero dramas.

The four-way crossover is expected to air in December. "The Flash" returns to The CW on Tuesday, Oct. 4, followed by "Arrow" on Tuesday, Oct. 5, "Supergirl" on Monday, Oct. 10, and "DC's Legends of Tomorrow" on Thursday, Oct. 13.