"The Dominators are coming! The Dominators are coming! Wait... who are the Dominators?"

That was more or less the outcry when The CW announced that the villains of this fall's four-part crossover between "Arrow," "The Flash," "Legends of Tomorrow" and "Supergirl" would be a semi-obscure DC Comics race of aliens. While their initial comic appearances came and went with little more than a blip on the radar, long-time readers know that the Dominators are one of the more dangerous alien races in the DC Universe, thanks to two prominent storylines in the late '80s and early '90s. More importantly, the arrival of the Dominators could spell huge changes for the metahuman population of all four shows.

Superboy and the Legion #243

RELATED: Arrowverse Crossover is ‘Very, Very Faithful’ to DC’s Invasion!

The Dominators first appeared in 1967's "Action Comics" #361, written by Jim Shooter and illustrated by Shooter and Jim Mooney. Initially, they were a somewhat lackluster alien race, appearing as little more than a MacGuffin; an alien race needing to be escorted, only to have another foe attack during the process. It wasn't until the Earthwar storyline running through "Superboy and the Legion of Super-Heroes" #241-245 in the late '70s that we saw them again; by this time, they were important enough of a power that the Dominion was just one of the forces being drawn into an intergalactic conflict along with Earth, the evil Dark Circle, the often-villainous Khunds, and even the sorcerer Mordru. Still, though, the Dominion were barely a presence in the comics, although their trademark yellow skin, oversized heads, and red circles on their foreheads were now front-and-center.

The Dominator Invasion!

Everything changed in 1989, though, when Keith Giffen not only brought the Dominators back, but did so in both the 20th and 30th Centuries. The first big storyline was the three-month crossover named "Invasion!" Touching on just about every DC Universe series at the time, as well as having its own central miniseries, "Invasion!" let Giffen, Todd McFarlane and Bart Sears feature the Dominators not only deciding to invade Earth, but teaming up with numerous alien races in order to do so. Their appearance was tweaked slightly, adding long, taloned fingers, and hideous teeth replacing the grill we'd seen earlier for their mouth. In other words, the Dominators were now out-and-out evil villains.

While each alien race had its own beachhead and attack plan, the Dominators were truly the masterminds behind the war. The idea was that humanity had a metagene in its DNA, and given enough time, too many humans would have that gene activate and gain so many superpowers that the human race would become unstoppable. Clearly, the best way to prevent that outcome was to attack first.

Invasion #2 Metagene

As the onslaught against Earth began to fail -- thanks to resistance from both superheroes and the world's armies, led jointly by Captain Atom -- the Dominators unleashed their final weapon: the Gene Bomb. When detonated, it scrambled the powers of many heroes, knocked most into comas (most notably Lodestone of the Doom Patrol, which used the "Invasion!" storyline to clean house of characters Grant Morrison didn't want as part of his and Richard Case's upcoming run on the title), and even resurrected the deceased Metamorpho. Ultimately, the non-affected heroes (mostly non-humans or non-powered heroes) were able to reverse the effects and revive the planet's metahumans. The biggest change, though, was that it activated the dormant metagenes of countless non-powered humans. In other words, the Dominators had created exactly what they didn't want to fight.

RELATED: DC’s Heroes Step Out in Photo Teasing Arrowverse’s Megacrossover

Up until now, metahumans in the CW's television shows have primarily received their powers through the S.T.A.R. Labs explosion detailed in the first episode of "The Flash." While it did a good job of keeping those heroes initially confined to that television show, if the series want to expand, a new origin will be needed. As part of this crossover, the Dominators may repeat history. What better way to expand the number of metahumans on these four shows than by detonating a new Gene Bomb to transform people across the entire globe?

Earth-Shattering Destruction

Impressively, though, the Dominators have done something even bigger than invade Earth as part of an alien coalition in the 20th century. But in order to explain that, you first need to jump forward in time 1000 years, into the 30th century, to the era of the Legion of Super-Heroes. Giffen was also masterminding the "Legion of Super-Heroes" series of that time, alongside writers Tom and Mary Bierbaum. Set in the controversial "Five Years Later" era -- where the series had jumped ahead in time five years and readers slowly discovered that the Legion had not only disbanded but been specifically barred from operating on Earth -- a slow reveal over the first two years of the series showed us that the Dominators were not only operating openly on Earth and were now part of the United Planets, but that they had secretly taken over Earth's global government and were the true puppet-masters behind the banning of the Legion.

Legion v4 #29

The story came to a head in a year-long saga running through the third year of the series; in a story titled the "Terra Mosaic," the Legion and its many allies finally took back the planet from the Dominators, even as wide-spread destruction and death hit in a relentless manner. From the genetic manipulations of prisoners to turn them into mindless slaves, to the assassination of Earth's president during a live broadcast, nothing was beyond the Dominators. But of all of the disasters that hit during that guerrilla-style war, it was a series of explosions beneath Earth's surface that proved to be the most disastrous. No sooner did the population of Earth catch its collective breath as they gained their freedom then the worst news of all came in: the explosions had caused a chain reaction that was eating its way towards the planet's core, and the Earth would soon explode. Ultimately, the Legion and the scientists of the United Planets were able to save 94 cities by using emergency domes and launching them into space to form a massive construction dubbed New Earth, but billions left behind on the planet perished as the planet was destroyed.

Since "Legends of Tomorrow" is a show that features time travel as part of its central premise, this major storyline set in the future may hold more weight than one might initially think. Hints that the Legion of Super-Heroes will make an appearance in one of the CW's shows have been flying fast and furious, most specifically on "Supergirl." What better way to fully introduce them than to have the Legends and friends jaunt a thousand years forward in time to fight the Dominators on the eve of their most deadly plan?

While plot points are still to be revealed, choosing a genetic-manipulating evil race surely can't be a coincidence. Whatever the reason, though, the Dominators in the comics were shown to be incredibly dangerous and deadly foes. The characters of the Arrowverse better beware: the Dominators are coming.