In a deleted scene from Batman v Superman posted by Warner Bros. shortly after their film's release, some sort of demon alien seemingly born of graphite and Michael Bay's Transformers briefly appears to show off these wonderful cubes he owns. The relevance and identity of said creature has been debated among people who still can give a shit what happened in Batman v Superman, but now we may have the answer.
According to BirthMoviesDeath, that's Steppenwolf--Darkseid's uncle; New God; military general of the hellish planet of Apokolips; unrelated to the late '60s classic rock group. And, though the iconic villain Darkseid himself was rumored to be the villain in Justice League, it's said that this guy Steppenwolf will first fight the group as the central antagonist. What a follow-up to the much-anticipated feud between Batman and Superman! Steppenwolf! But not the band!