Producer Deborah Snyder confirmed that Steppenwolf will be the primary antagonist in next year's Justice League movie, although the actor who will bring him to life has yet to be cast. The film doesn't get released until November 17, 2017, so they've still got a while to get an actor in place.
Created by legendary writer Jack Kirby, Steppenwolf a member of the New Gods, a race of immortal, an cosmic beings, so it looks like the League will have their work cut out for them.
Justice League stars Ben Affleck as Batman, Henry Cavill as Superman, Gal Gadot as Wonder Woman and Ezra Miller as the Flash.
Sources