Black Flash

The Black Flash is a supervillain in the DC Comics universe who is actually one of the many embodiments of Death itself - though Black Flash only goes after the souls of people who possess superhuman speed connected to a special power known as the Speed Force. Created by writers Grant Morrison and Mark Millar, and artist Ron Wagner, the character had cameos in The Flash vol. 2 #138 (June 1998), before appearing in full in The Flash vol. 2 #141 (September 1998).

It is unclear why Death takes on the form of Black Flash to track down speedsters - though some theories are made that either top-rate speedsters (such as the Flash) are too fast for traditional Death to catch up with or that Black Flash is a result of some kind of anomaly caused by the Speed Force itself, whatever the cause Black Flash exists for one purpose: to end the lives of speedy heroes and villains in the DC Universe.

It should come as no surprise that the Black Flash was an enemy of the Flash (both past and future-versions) but his appearances are fairly rare - as was the case for most personifications of death, after all the arrival of the Black Flash usually suggests that Flash is about to die or in serious danger of doing so.

Though unlike most versions of Death, the Black Flash is capable of being defeated or at least stalled so not all encounters with the entity need be fatal to a speedster, though a victory against a being like Black Flash is likely in vain as he will keep coming back until his job is done. Black Flash was killed off a long time until he made his return in DC Rebirth.

An original incarnation of the Black Flash appears in TV series set in the Arrowverse. This version was originally Hunter Zolomon / Zoom, who was transformed by the Speed Force and made to serve as its enforcer by hunting down speedsters who attempt to change the timeline and erase his targets from existence.