The Flash season 2 finale saw the nefarious Zoom transformed into the Black Flash aka the Black Racer. In the comics, this character is an embodiment of the Speed Force that takes Speedsters to the after life upon their demise as the traditional embodiment of Death is too slow to catch them. Zoom's transformation initially had many fans theorizing that the Black Racer could play a major role in season 3 but that was before Savitar and Dr. Alchemy were confirmed to be this season's major adversaries.
However, that doesn't rule out the possibility of the Black Flash showing up somewhere down the line, a sentiment echoed by Zoom actor Teddy Sears. "Zoom has been transformed into Black Flash, who has quite a place in the mythology of The Flash. He’s like the grim reaper for speedsters. Andrew Kreisberg, the head writer and EP, has talked about their interest in having a Black Flash return at some point in the series."
Yet, with Sears currently busy on the Fox series 24: Legacy, which presumably keeps him from appearing on The Flash. “It would be a lot of fun to drop back into that world. We’ll just have to see if the guys on the other end feel the same way. It sounds like they do, but it’s funny – now I belong to Fox, so there’s lots of people that would have to give a thumbs up. But I really hope so."
The Flash season 3 returns from midseason hiatus on Tuesday, January 24 at 8/7c on The CW.