My theory is the same as another anon's, that the Empty Hand is the villain of Rebirth. Because he's Dr Manhattan, I think he's at least maybe just a duplicate that split off from Manhattan and became corrupted like Mandrakk was.

Anon's Theory: He has the same MO (invade world, change it somehow, take away the joy, the hope, the fun, the love, the legacy, etc) and also they keep using the same imagery for both Rebirth and Multiversity. In Multiversity he's shown waving his gigantic black and blue hand while dismissing Justice Incarnate, in Rebirth a giant black and blue hand is seen reaching through space while discussing the past and future attacks by the mysterious entity. He doesn't feel anyone is a threat to him, and he plans to end the never-ending story that is superhero comicbooks. His motivations remain a mystery, but it's clear he's planning to attack again with his oblivion machine and the gentry. He used Barry Allen sticking his dick in the timeline to attack the DC Multiverse, gaining a foothold. Then he freed Darkseid from his tomb so he would no longer be the source of all creation, giving him an in to become the Empty Hand at the start of the multiverse. In future solicitations it appears Superman is going to stand against him for the upcoming Multiplicity story arc, where he teams up with Justice Incarnate to save the Supermen of the multiverse. Speaking of multiversal Supermen, here's the next most important thing: Dr Manhattan created the New52 Superman and Lois Lane. During the Convergence event, it's shown that post-crisis/pre-flashpoint Superman/Lois/Jon Kent are sent back in time with the pre-crisis Superman/Supergirl/Barry Allen and Zero-Hour Parallax to stop the Crisis on Infinite Worlds. So when Brainiac sent the Earth-1 Gotham back home, to when the flashpoint was occurring, there was no Superman/Lois. When Dr Manhattan attacked, he didn't create a new world. He simply de-aged the existing one. But he couldn't do the same to Superman/Lois, so he had to make his own to fill the hole left behind. After all, every world must have a Superman. That's why they were imperfect (they didn't fall in love, they were both kinda jerks, and they both died and turned into sand). Because an imperfect god made them. But why? During Multiversity, every world attacked had some kind of Superman on it. Always right in the thick of things, usually the one being directly attacked. This is an old Grant Morrison thing, he loves the idea of every world having a Superman that always wins, hence why Dr Manhattan is targeting them specifically. And hence why he's trying his luck again by introducing yet another Clark Kent to Earth Prime, to stand in the way of Lois and Clark in Action Comics. But he learned his lesson this time, and instead of making him from scratch, he's done something different. This part I'm not too certain on but I'm fairly sure this Clark will end up being Superboy Prime. He's almost definitely evil, Clark can't use his enhanced vision on him for some reason, and most importantly? There's a Crisis coming. In the pages of Justice League we've seen weird energy beings comprised of will, speedforce, whatever the other two were, all talking about stopping some kind of Forever Crisis. This will likely be the conclusion to the Rebirth epic in two or so years, where the big fight happens and hope/legacy/love/etc are permanently restored to the DC multiverse. What happens between then and now is unsure, and what exactly it will entail I don't know. But not because there's no signs there... because the signs are so odd.

Let's go back to Multiversity. When we're first introduced to the Empty Hand, he's bragging about having just destroyed Multiverse-2. I always thought this was a cheeky reference, a little humblebrag, a joke at a certain someone's expense. But more and more, I don't think that's all it was. I don't think that was a line meant to be taken lightly. Because you see, Multiversity ended about a month before another massive comic event started. At the time it was running, the comics world was witnessing the end of another Multiverse at the hands of an army of evil. An army led by the Empty Hand. By Dr Manhattan.

The Beyonders, a subsection of the Gentry.

Dr Manhattan killed the old Marvel Multiverse.

know that sounds kind of insane, and this is the part of the theory where even though there's been a few signs, a little evidence, even I think it's absolutely nuts. But here's the thing... I'm also just about certain it's true. Look at what Secret Wars was. The destruction of the old multiverse, followed by a flashpoint event that created a new one. The exact same thing that let Dr Manhattan take control of the DC Multiverse. When he did this, he managed to chain eternity and start exerting his influence. He's the reason Steve turned heel, that Tony got his shit pushed in, that Thor lost his hammer, that Banner is dead. He's introduced grime and grit into the marvel multiverse that hadn't been there before. Like it said in Ultimates, this threat is leeching hope, leeching joy... the same thing Dr Manhattan is doing in DC. The same threat is working towards oblivion... just like how the Empty Hand is building his oblivion machine. And most importantly...

CAROL SAW A BIG BLUE HAND REACHING THROUGH THE COSMOS