TV Shows: The Flash - The Black Flash (Time Wraiths?)
All you need to know about the black flash is in this video: https://youtu.be/S0TCoQ1Bp_M
Who is the Black Racer?
We do know that he is a representation of Death for speedsters. It is also known to be connected to the Black Racer... actually he might actually just be the Black Racer.
Not included in the video is the Black Flash's initial defeat. (He was used against Darkseid later on. 52 did a rehash of it which made Barry the Black Flash again.)
The Black Flash's initial defeat: