Black Racer is New God, who is their Avatar of Death. His corporal form is that of the bedridden Sgt. Willie Walker, who was paralyzed during the Vietnam War. When Darkseid brought his war against the New Gods to Earth, Walker became the Black Racer, whose job is to collect the New Gods upon their death, and take them to Hadis, their version of Hades. Black Racer travels on his skis, taking the collected souls to Hadis.
Black Racer hasn’t really appeared in any stories outside of anything dealing with the New Gods. He is one of the first prominent African American characters in DC Comics. You can read more about Black Racer here.