Who he is: The Flash, a.k.a. Barry Allen
His power: The Flash can use his connection to the Speed Force to move at velocities faster than the human eye can follow. Some versions of the character also seem to be able to travel through time.
His story: In Batman V. Superman: Dawn Of Justice, Barry Allen is briefly glimpsed as part of Lex Luthor’s metahuman research, depicted stopping a convenience store robbery on closed circuit TV. A different version of the character, meanwhile, apparently invades a nightmare being had by Bruce Wayne, ordering him to “find Lois Lane” and bemoaning that he’s arrived “too soon.”
Played by: Ezra Miller
Currently, The Flash is: Living friendless in Central City and/or bouncing his way through time.
Where will see him next? Justice League.