From Batman News:
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According to /Film, Justice League was originally going to end with a big cliffhanger with Darkseid arriving to Earth, setting him up to be the main villain for the sequel. Now that ending has been completely scrapped. /Film says that Wonder Woman actor Robin Wright shot a new flashback scene explaining who Steppenwolf is. The looming threat of Darkseid is being downplayed with the reshoots.