The Dominators, collectively known as the Dominion, an ill-intentioned alien race from the fringes of the DC Universe are the threat requiring the combined might of Team Green Arrow, The Flash, Supergirl and The Legends of Tomorrow crew. Deadline reports that the Dominators arrive on Earth under the guise seeking to quell the rising population of superheroes before they can pose a threat to their plans for the rest of the universe.
In reality, the Dominators are on Earth to capture and study those who possess the metahuman gene in an effort to create the same phenomenon in their own race. Fans of Young Justice will recognize this as a similar plot for the show's second season with The Reach occupying the role that the Dominators will play.
What do you think of the news? The showrunners have definitely made a surprising choice for the threat spanning across all four shows. Arrow producer Marc Guggenheim told Deadline that a combination of "cutting-edge prosthetics and computer effects" will be used to create a feature-film quality aesthetic for the invading aliens.