So, basic speculation on what we got... superpowers, and possibly a majority of magical artifacts, are tied into this mystery metal, which SEEMS to be from another dimension. Probably the Dark Multiverse we've seen mentioned.
Speaking of the Dark Multiverse, it'd kind of looking like Snyder's setting up an interesting take on an Extinction Trap scenario, where higher progress destroys civilization but expanded to include the entire multiverse, apparently.
Meanwhile, Joker seems to be stuck in a time loop.
The Hawks got tied back to the Batman RIP Cave-Batman material. Interestingly, the actual Bat-Clan seems to have been morphed into villains.
Curiously, we've gotten a look at two seemingly distinct major antagonists - the "True Father of Batman" who looks suspiciously like Darkseid in a hood, and the giant three eyed demon thing. Could be a riff on Final Crisis, which split between Darkseid and Mandrakk in a similar way.
Savage and Sam are more or less explicitly called out when the Immortals were being described.
I wonder if these people were in the cloaks.