Who is Black Flash, and why is he on Legends of Tomorrow instead of The Flash?

The threat that plagues Eobard Thawne on Legends of Tomorrow isn’t a new one to fans of The Flash on TV or in comics.

This week’s episode of Legends of Tomorrow gave us something that some fans have been waiting for all season: the true formation of the Legion of Doom, with all three villains as partners. Ironically, it took Black Flash to bring them together.

Not that Eobard Thawne, Damien Darhk or Malcolm Merlyn called the Speed Force-sniffing monster by that name. It fits though, since viewers of The Flash almost certainly know who that used to be and why he’s clad all in black.

Let’s take a super-speed sprint back into comic book history first.

Black Flash in DC Comics

A product of the fertile imaginations of writers Grant Morrison and Mark Millar with some assistance from artist Ron Wagner, the Black Flash was presented as the personification of Death for beings connected to the Speed Force. It showed up at various times in the life of Wally West, who was able to evade it, and Bart Allen, who was not as fortunate.

Perhaps his most interesting appearance was in The Flash: Rebirth series in 2009-10. That story saw Barry Allen himself become the Black Flash (memorably disintegrating Savitar, though it was by accident) and making his touch deadly to other speedsters. Thanks to help from other Flashes and their friends, Allen was able to defeat the Reverse-Flash, whose machinations had caused his transformation in the first place.

Black Flash in the Arrowverse

Season 2 of The Flash introduced the concept of Time Wraiths, creatures who enforced the natural order of time by pursuing those who mess with it the most. The Time Wraiths caught the scent of Barry Allen a time or two, but were more interested in Hunter Zolomon: the villain known as Zoom, who had misused the Speed Force and time travel quite a bit.

In the season 2 finale, the Time Wraiths arrive during the episode’s climactic scene and finally catch up with Zoom. As they drag him back through an interdimensional portal, his flesh started getting torn from his face, leaving him with the skeleton-like appearance that Black Flash usually sported in the comics.

Obviously, fans who guessed Zoom had become the Black Flash were correct. Now the big question is why he’s after Thawne. The Legends filled in some of the blanks for us by reminding us that Reverse-Flash ceased to exist after Eddie Thawne took his own life in season 1 of The Flash. Barry brought him back during his actions that caused the Flashpoint timeline, but that has since been mostly corrected again, and Thawne exists only as a time aberration.

He’s desperate to find the Spear of Destiny on Legends of Tomorrow to rewrite reality so he can stick around. Hard to blame him for that. The problem is that he has Black Flash on his tail, possibly because the Speed Force figured it needed something more formidable than the Time Wraiths to catch the rogue speedster.

Next: The Flash has a super-quick Supergirl crossover

While terrifying in appearance, Black Flash isn’t a bad guy so much as a force of nature. The Legion of Doom was able to cooperate long enough to slow him down this week, but he’s bound to keep pursuing Reverse-Flash for the rest of the season. And that trick he used to stay still won’t prevent him from carrying out his mission forever.