We know Darkseid is basically confirmed for the DCEU, but what we don't know is how he'll make his presence known. The Knightmare Batman and the Superman troops are all still a major fucking mystery. And with the Empire Magazine of Batman looking over the OMEGA symbol burned into the ground is still one of the greatest images I have ever seen.
My theory as to how it all plays out is maybe the reason Wonder Woman is in the movie in the first place is she's looking for a weapon to destroy Darkseid. My guess is during her search for said weapon, she gets entangled in Lex Luthor's little game of war with Batman and Superman.
How it all plays out according to me:
Diana finds out that Lex has the weapon she has been looking for. Which is an ancient weapon that is powerful enough to kill or subdue Darkseid. During her investigation to prove her suspicions, Mr. Wayne comes out of nowhere. They meet and talk because he somehow deduces she is looking into LexCorp. However he has no clue what. During their meeting at the dinner parties he tries to sway her into giving him answers but she refuses to give in.
After a few encounters with Bruce as Batman or as the playboy, she has a dream or a vision of the future. And that's where Knightmare Batman comes into play. She sees that Mad Batman survived the onsalught by Darkseid. He is the only surviving human because he's fucking Batman.
Furthering into the dream/vision, she sees Batman try to infiltrate Superman's soldier compound for weapons, but he is caught along with followers. Or they could just be scavengers like he is.
Superman has formed an army to combat Darkseid and he doesn't appreciate Batman interfering. Maybe he wants Bruce to follow his orders rather than the other way around. It's either Superman's way or nothing.
End dream sequence because I have ran out of ideas.
So Diana wakes up from her dream/vision and tries to locate Batman and Superman to warn them of the incoming calamity that is Darkseid. As she searches for a way to reach them, they are in the midst of their battle. They are beating each other to near death before she steps in and puts them in their place.
She warns them of Darkseid which eventually leads them to put their animosity against each other to bed. As Wonder Woman, Batman, and Superman are conversing with one another about the big baddie, Lex is creating Doomsday. As they speak, Diana mentions Lex which leads Batman or Bruce to chime in about Luthor. Maybe during his break-in for the kryptonite or whatever he discoveres plans of creating something out of Zod's dead body. Which causes Superman to fly over and confront Lex.
When Superman gets to Lex, he finds out that he has Lois hostage. During the whole Batman and Superman fight, Lex was in the background watching. When he sees that the two have settled their differences, he moves quickly with his plans. He sets off to kidnap Lois and create Doomsday. He forces the three heroes to fight his creation in order to save Lois.
As the heroes battle Doomsday, Lois manages to fight off and make an attempt at escaping. She runs through his lab knocking shit over and eventually comes across another kryptonite rock. When Lex is about to catch her, she dodges and locks him inside the room with kryptonite. The radiation starts to kick in and he begins to weaken. He falls to the ground and sees himself begin to bald.
Outside somewhere probably in an abandoned island, Doomsday is roughing up the heroes. Batman is down and Wonder Woman is as well. Superman is still standing, but nearly broken. He looks around and sees his friends down then he hears Lois's voice. Superman then makes the decision to sacrifice himself in order to protect everyone. He flies up into space and then dive bombs at unbelievable speeds toward Doomsday as they blast lasers at each other. Which creates that big ass explosion we have seen over and over. Superman causes Doomsday to use his laser beams to max which causes him to like explode from overuse of his power. Just as he explodes Superman is like caught inside of it and the blast nearly kills him because Lex somehow mutated Zod's body with the help of Kryptonite. Rather than just a normal super laser explosion; it is mixed with Kryptonite.
Superman then falls to the ground nearly dying when Batman and Wonder Woman recover. Batman has no idea how to save him, but Wonder Woman does. She flies off with him to Themyscira to have her people help heal him.
Then the ending is the possible montage of the Justice League coming together. Well that's my theory guys. What do you think? Cool? Awesome? Amazing? Shit? Don't ever write again? Give me your opinion in the comments below!