Orion (or possibly another New God)
Who is he: Now in the comics, Orion is actually second son of Darkseid, but he was traded for Scott Free as a child through the means of a treaty arrangement between New Genesis and Apokolips. In various media he is always coming as a precursor (or sometimes as a means of defence) to where Darkseid is planning to attack.
Why its possible: With the final act of Batman V Superman: Dawn Of Justice laying some heavy handed hints that Darkseid is coming, its highly likely that Orion will be arriving soon.
