Ben Affleck is currently in London, filming the Justice League - which will see him reprise his role as Batman.
He took a break from shooting to post this vague 30 second video to twitter, showing DC Universe villain Deathstoke walking menacingly through the frame. Deathstroke / Slade Wilson is a solider, who is given powers thanks to secret army experiments.
— Ben Affleck (@BenAffleck) August 29, 2016
The video was not captioned, so it's not clear if the footage is for The Justice League or for Affleck's own Batman project. However, The Wrap has reported that Deathstoke will be the main villain in the standalone Batman film, which Affleck is directing as well as starring in.
The Justice League is scheduled for a November 2017 release, and will be directed by Zack Snyder. Batman has no scheduled release date yet.