[KaVir]

It's a fictional setting, but I deliberately tied in a mixture of different real-world mythology (primarily Greek and Norse, but there are others too) to imply links with prehistory earth.

I didn't write it up in advance (other than some basic notes), but instead created it a bit at a time as new content was added. Each new quest added a little history, and I tried to connect them together when possible. There's no "complete history" that people can read, but as they explore the content they gradually learn more about the world.

The latter - if anything, the history is more of an accidental by-product of needing flavour text for quests.

The latter - the history has taken shape as a direct result of new content being added.

The history is primarily based on religions, due to the theme of the mud.

Note that my mud is explicitly non-RP, so the history isn't as fleshed out as one would expect from an RP-focused mud, nor was there an urgent need to create the history in advance. But IMO all muds can benefit from an internally consistent theme and some background flavour.