The Legacies premise is pretty straightforward:
- They Began When They Began. The characters of the DC Universe each started their active adventuring career on or about the same time as their first appearance on the comics stands in our world.1
- Life Happens. They aged normally2 from that point, and had full lives. Many of them married and had children, sometimes with ordinary people, sometimes with other superhumans or costumed adventurers.
- Dead Is Dead. If a character died in the comics, they stayed dead, even though the comics eventually brought them back.3 No miraculous resurrections.4,5
- The Gang's All Here. "Characters of the DC Universe" includes pretty much every character currently under the DC umbrella, including the original stable of National Allied Publications (Superman, Batman) and All-American Comics (Green Lantern, the Flash), Quality (Blackhawks, Freedom Fighters, Plastic Man), Fawcett (Shazam!), Charlton (Captain Atom, Blue Beetle, the Question), Milestone (Icon, Static), MLJ/Red Circle (the Shield, the Web), and Wally Wood's T.H.U.N.D.E.R. Agents.
- All This and Arkham, Too. In the Legacyverse, the traditional DC "fictionopoli" do not co-exist with the cities of our world; they replace them. Gotham City is Boston, Metropolis is New York City, Gateway City is San Francisco, and instead of Los Angeles, there's a big crater where Coast City used to be. Fictional locales from sources other than DC comics are likely to make an appearance; the suburbs of Gotham include Arkham, Kingsport, and Innsmouth.
- "Guardians of the Universe" is a misnomer. Oan jurisdiction extends across the "region of dominant gravitational attraction of the Milky Way Galaxy", including the halo of globular clusters surrounding it. As far as is known on Earth, the Magellanic Clouds are "disputed territories". Just who would dispute such matters with the Oans and the Green Lantern Corps is a matter of endless speculation in xenopolitical circles.6 For the record, there are a lot more than 3600 sectors in the Oan Jurisdiction, though I haven't decided just how many there really are.
- Big Events Usually Happened. Events in the Legacyverse track the main DC timeline(s) fairly closely, right up until the Crisis of 2008 ("Final Crisis"). The various alien invasions, the Luthor presidency, the Gotham Earthquake, the destruction of Coast City -- they've all left their mark. Not all of them did, though, and they didn't all happen in the same way. There Will Be A List Later.
- Yes, Virginia, There Is A Multiverse. It's ... wider, weirder and more diverse than the one we see post-52, though. Since the mid-1960s, the Justice League have had annual contact with a team from a parallel Earth that call themselves the Avengers ... .
- Some Elseworlds are Thisworlds. Oddly, while John Byrne's Generations shares almost exactly the same premise, I wound up using very few of his plot twists. I'm using a few bits from Darwyn Cooke's New Frontier (especially Diana's costume!), and a whole lot of James Robinson's The Golden Age.
- It All Started With K-Metal. This is important enough to give it its own bullet point: "The K-Metal from Krypton" is an unpublished Shuster and Siegel tale from 1940; Joe and Jerry originally planned to have Superman discover his origin and reveal his identity to Lois early on. Please read this; for one, it's a short, fun tale; for another, it's exactly the point where the published stories of the DCU diverge from the Legacyverse timeline.7
- There are exceptions to all of these rules, of course. Green Arrow, for instance, doesn't put on a costume until the late '50s, while his comics counterpart first popped up in the '40s. His Bronze Age Road Trip with Hal Jordan and his relationship with Black Canary are just too important, and he needs to be the right age for that.
- "Normally" as modified by alien or metahuman physiology, of course.
- There will be exceptions here, too. Not every death scene "counts".
- Things like Lazarus Pits aren't "miraculous" if they're an established part of a character's background. Ra's al Ghul isn't known for sharing, though.
- Yes, this means that a lot of familiar young faces will be in their 70s, 80s, and 90s. More than one regularly-appearing character in the comics will be, well, just plain dead.
- For some reason, I never had to worry about stuff like this in Gotham.
- You might notice that "K-Metal" has properties not normally seen in the Green Kryptonite that later appeared; those properties may be a plot point.