Following his battle with Doomsday in Batman v Superman: Dawn of Justice, Superman sacrificed himself to kill the Kryptonian abomination. But that wasn't the film’s only major twist. The Communion clip revealed the existence of Apokolips and of the Mother Boxes, which will serve as MacGuffins in the first DCEU ensemble movie. The clip also revealed a villain who would later be the first Justice League film’s main antagonist.

Want more details on the connection between the Communion clip and Superman’s death and resurrection? Here are some spoilery details, as revealed by producers Curtis Kanemoto and Jon Berg!

According to Kanemoto, Superman’s death is noted throughout the universe. In one of the Justice League trailers, Steppenwolf observes that there’s no Kryptonian left to protect Earth after the news of Superman's death wakes a Mother Box (the one in the possession of Men), which then transmits a signal to Steppenwolf. Now the villain is back to collect the powerful artifacts:

Superman’s death has awakened a Mother Box. One of these exists in man’s world, one exists on Themyscira, and one in Atlantis. When one of these Mother Boxes Awakens, it calls to Steppenwolf, our villain, and he arrives to collect them. The story borrows from the world of Jack Kirby, who created the New Gods. Zack Snyder, Geoff Johns, and Chris Terrio have done an amazing job integrating the Apokoliptian tech into the world of Justice League (via CBM).

Berg said that Steppenwolf has already made one failed attempt to conquer Earth. Now, after thousands of years, he’s back to finish the job:

He’s a warrior from another planet who tried to conquer Earth a few thousand years ago and failed. He’s been living with the disgrace of having failed, and desperately wants to avenge his previous loss.

We don't know why he didn't come back while there was still no Man of Steel on Earth. If Krypton played a part in defending Earth during the first assault, the general from Apokolips still had a window of opportunity between the destruction of Krypton and when Clark Kent became aware of his ancestry.

We Got This Covered recently reported that, as rumored, the genesis pool, Flash's powers, and a Mother Box bring about Superman’s resurrection.

His resurrection comes courtesy of a number of factors, namely the genesis pool from his Kryptonian ship, an Apokoliptian Mother Box, and a spark provided by The Flash. Once they get this figured out, the League get out the shovels for some good old-fashioned body snatchin', and exhume his corpse. Fortunately, his Kryptonian DNA means he hasn't decomposed, so they zap him back to life. Unfortunately for the team, though, Superman is a little grumpy and confused about being returned to the world of the living, something not helped by Cyborg's defense systems zapping him.

It seems a bit convenient, doesn’t it?