WARNING: The following contains spoilers for Star Trek: The Next Generation - The Mirror War #0, available now from IDW Publishing.
IDW Publishing's Star Trek: The Next Generation - The Mirror War is a year-long event that will follow an evil version of Captain Jean-Luc Picard as he continues his quest for complete domination of the Mirror Universe, an alternate reality populated by darker, meaner versions of iconic Star Trek characters.
After a failed takeover of the Prime Universe's Enterprise D, the Mirror Reginald Barclay was thought dead. But after learning of his survival, Picard and the Mirror Universe crew stoke the fires of war. However, the Mirror Universe crew just recovered Barclay in Star Trek: The Next Generation - The Mirror War #0, by Scott and David Tipton, Carlos Nieto, Dc Alonso and Neil Uyetake, setting the stage for the titular conflict to start in earnest.
Star Trek has a long and tumultuous history with the Mirror Universe, beginning with the iconic Original Series episode "Mirror, Mirror." In this episode, the crew of the Enterprise meets their evil doppelgangers from an alternate universe, which is run by a fascistic version of the Federation known as the Terran Empire. While Captain Kirk and his crew would ultimately come to beat their evil doppelgangers - and overthrow the Empire - the episode would go on to become a firm fan favorite.
After becoming a staple in Trek novels and comic books, the Mirror Universe eventually returned to television in the Deep Space Nine episode "Crossover." There would be a total of five Deep Space Nine Mirror Universe episodes, in which it was revealed that the universe was now under the control of an equally brutal, militaristic Klingon-Cardassian Alliance. While the Mirror Universe also failed to make an appearance in Voyager, the Mirror Universe would appear in Star Trek: Enterprise and play an integral part of Star Trek: Discovery's first and second seasons, where several Mirror Universe characters spent time in the Prime Universe.
While The Next Generation never got its official Mirror Universe episode, IDW Publishing first introduced the ruthless crew of the ISS Enterprise in "Mirror Broken," and its sequels, "Through the Mirror" and "Terra Incognita." These Mirror Universe misadventures would introduce the ruthless Captain Picard and his equally cold-blooded crew.
In "Through the Mirror," members of the Mirror Universe crew attempted to hijack the Enterprise D for their own evil machinations. When this failed, they were forced to retreat, leaving their version of Reginald Barclay for dead. Unbeknownst to Mirror Picard, Barclay had in fact survived, and was posing as his doppelganger, who he had overpowered and was holding hostage. When he learned of Barclay's survival, Mirror Picard was incensed, and immediately sent an away team to recover their crewmate in Mirror War #0.
While the idea of anyone going to war over the incompetent, ridiculous Barclay - even a darker, more competent counterpart - seems absurd, this only goes to show how petty the inhabitants of the Mirror Universe can be. While the recovery of their crewmate certainly gives Mirror Picard's crew a tactical advantage, it is notable that Picard's first thought isn't for tactics, but rather petty revenge. But with their Barclay armed with intimate knowledge of the Enterprise's inner workings - and, thanks to his time in the Prime Universe, the Klingons and the Cardassians too - this gives Mirror Picard a tactical advantage over his own enemies within the Mirror Universe.
The Mirror War will see Mirror Picard and his crew using their Prime Universe intel to launch a full-scale assault upon the Klingon-Cardassian Alliance. Armed with Picard's ruthless aggression and Barclay's unique insight, the ISS Enterprise crew have made themselves a force to be reckoned with, in whichever universe they happen to reside.