Not exactly a new character here, but a long-awaited confirmation. At the end of The Flash Season 2, in the episode The Race of His Life, the villainous Zoom ended up prey of the Time Wraiths, and before being dragged into the Speed Force he had his appearance quite changed, with his face reduced to a grinning skull, his mask ripped and his emblem turned white and red. Many fans recognised his new appearance as the one of the Black Flash, the most feared enemy of every Speedster…and according to a recent interview to John Wesley Shipp and Mark Guggenheim they were right, as it’s been confirmed that Zoom, as a punishment for his manipulations, is now forced to serve that very Speed Force he tried to cheat as the Black Flash. In the comics, the Black Flash is not an alias of Zoom, but this makes him only more fearsome, as he is a totally supernatural being. Let’s see together.
The true origins as the creature known as the Black Flash are quite ambiguous. According to most sources, the moment the first human tapped into the Speed Force becoming a Speedster, Death found out that mortals had become faster than she was, and it had become impossible for her to reach them. Everyone must die eventually, and just as she had done with other races, species and categories, she created a new form, one specifically designed to catch the uncatchable Speedsters: the Black Flash, the Grim Reaper who was just as fast as the fastest man alive. According to other sources, the Black Flash was born within the Speed Force and belonged to it: he was the personification of the negative energy that accumulated inside the Speed Force itself, and when someone tapped into the Speed Force using its energy to gain the incredible speed it granted, he was the one who appeared at the end of their lives to claim them, so that they could give back the energy they had been using. Being it a way or the other, the appearance of the Black Flash meant death for whoever saw him, hero or villain, as long as they belonged to the Speed Force. It wasn’t necessary that said Speedsters died directly at his hands: he just claimed what belonged to the Speed Force, whether he was the cause of their death or not. When the second Flash, Barry Allen, sacrificed himself to save the Multiverse, the Black Flash was there to take him; when Johnny Quick consumed himself in the effort of stopping his nemesis Savitar, the Black Flash was there as well. He even appeared more than once to Max Mercury, who got close to death many times: any time he risked his life, the veteran hero clearly saw the Black Flash running besides him, trying to take him. He avoided death every time, and as result the Black Flash stopped chasing him, but it was only a matter of time: the Black Flash eventually caught everyone.
The Black Flash eventually came for the third Flash as well, Wally West: during their first confrontation, the Scarlet Speedster managed to escape him, but upon returning to the Speed Force the Black Flash inadvertently took along Flash’s fiancé, Linda Park. When he returned once again to collect the right person, he froze time for whoever was not connected to the Speed Force, so that he could point his target only…but he found a small army of Speedsters waiting for him nevertheless. Along with Wally West, there were also the first Flash Jay Garrick, Max Mercury and Jesse Quick, who tried to slow the Grim Reaper down to allow Wally to find a way to defeat him. The Black Flash ignored the three heroes just as long as they weren’t a direct hindrance to his hunt, and focused on Flash only: Wally ran away, letting the Black Flash follow him. They were so fast that they travelled through time, but as fast as Wally could run, the Black Flash was always a few steps behind him, never slowing down, never getting tired. Then, finally, the Flash reached his intended destination: the end of time, a limbo in which time as we know it reached its ultimate consumption…the only spot in space-time in which Death had no place nor meaning. Tricked, the Black Flash dissipated, and Wally earned the right to live more than the Speed Force had decided for him. Of course, Death could not disappear, and the Black Flash was but an aspect of her: he reformed soon after, ready to resume his duty. When, some years after that episode, Bart Allen became the fourth Flash, and he was ultimately killed by Inertia and her Rogues, the Black Flash was there, “alive” and well, ready to collect the energy of yet another Speedster.
The Black Flash, whether he’s a manifestation of Death or the dark aspect of the Speed Force, is a relentless being who exists only for his hunt. He is just as fast as the Speed Force allows to be (that means something like four times the speed of light), with all the superhuman abilities deriving from super-speed; he also possesses some degree of chronokinesis, as he’s able to freeze time for whoever’s not connected to the Speed Force. With no pity, no remorse, no emotion whatsoever, the Black Flash is unstoppable, immortal, an omen of death for every Speedster, inescapable just as the fate he represents.