I have not seen it, it is on my "too lazy to seek out but I will see it if it is on the telly" list.
Well, where do I even start? First some quick background info, which Im not even 100% sure if it is correct by now...
The DC universe got a giant wall at the end of the known universe known as the Source Wall. The ones that have tried to penetrate it to see whats on the other side have been stuck in it and been transformed into a part of it.
The comics published between 1938 -.1950 are called the Golden Age of comics.The comics published between 1956 - 1970 are called the Silver Age of comics.
DC used to have many many many alternative universes back in the days. Just to mention a few...
At the Silver Age, most of the DC characters got a rebooted backstory to make them more interesting. In Batmans case, he turned from the Adam West Batman into something more darker and returned to his detective roots. But they also continued to publish stories about the Golden Age versions, and let them turn older. In Batmans case, he married Catwoman, got a daughter named Helena Wayne (who would grow up to become the Huntress), and he died in a battle against a super villain. This universe where the Silver Age versions existed was called Earth-One, while the universe where the Golden Age versions existed was called Earth-Two.
Earth-A was an alternative version of Earth-One where every superhero are evil and ruled the world.
And then we got some really crazy ones. Earth-C is populated by anthropomorphic "funny animals", think of it as the DC version of Bugs Bunny. Earth-C-Minus is the same as Earth-One with the exception that everybody are anthropomorphic "funny animals", and everything that happened here appeared as comics in Earth-C. And then we got Earth-C-Plus which is another set of anthropomorphic "funny animals" which originates from the Fawcett Comics stories.
Some universes were used once or twice while others were used multiple times, and it was a mess trying to figure out exactly what was canon or not.
Even the comic creators got confused, which resulted in some continuity errors. Like Black Canary of Earth-One being the daughter of the original Black Canary of WWII even though the original Black Canary was a resident of Earth-Two.
So to solve this mess, and making another reboot, DC created the Crisis on Infinite Earths event in the 80s, which basically destroyed the whole multiverse except for five universes, which was later used to recreate a single universe.
As time went on, DC couldnt keep their hands away and started to create oneshot alternative universes again. And then in 2005 they started their big event called 52, which basically gave us 52 different canon universes.
And then they decided to fuck things up some, making every DC story that have ever published be canon no matter how impossible it is, retconned away the Crisis event, did some other crazy stuff, still kept the numbers of universes at 52 and made DC Rebirth in 2016.
Anyway, to make it an even messier mess, DC have just had the Dark Nights: Metal storyline which basically tells us that each multiverse got a dark counterpart which exist for a "short period of time". Basically it was used as an excuse to have multiple evil versions of Batman morphed into different members of Justice Leage or villains, like one being as fast as Flash, one being turned into a Joker, one being a copy of Doomsday, etc.
At the end of this storyline, the Source Wall started to crack and our extremely powerful beings appeared and started to harvest life from different planets. The good guys had to team up with the bad guys to defeat them and survive, and multiple subsets of Justice Leagues were created. Then Lex decided to run his own race and left with the villains. It seems like the Source Wall was there to hide and protect them from a much bigger universe and at the same time serve as a prison for a sleeping overpowered Goddess which Lex decided to try waking up because he believes that he can trick her into giving him the knowledge of the universe and everything, and Justice League doing everything they can to try atopping him.
...damn, that was a lot to type...
Speaking about videos, I finally got my hand out of my ass and borrowed those movies. It was 12 of the 17 ones that I wanted and 11 bonus movies.Better than expected, but still a little bummer that it didnt include the movie I was looking most forward to watch again.