I'm committed to the world. One I've used before. It's high medieval, verging on the renaissance, lacking only gunpowder. Norse based invaders over-running a rain forest covered island and conquering the bronze-wielding, pseudo-Celtic people to establish a number of kingdoms in the highlands of the island. A period of eight hundred years or so passes and it's a much more modern time then it was when the Redhand waded ashore and founded his city dedicated to the War God Tyr. A second wave of invaders has arrived enslaving the northern tribes, loosely based on the Babylonian mythos, inhabiting a as yet unfinished city in the classic autocratic eastern model, filled with slaves which have a religious hatred of Dwarves and Gnomes.
(Yes it's the idly sketched map you go just go with)
Yes that Dark Elf Empire up there is roughly sketched in as corrupted by Demons. The elves on the main island would be either high elves or wood elves, with varying magic. The races tend to keep to themselves, the halflings are unknown in the human lands, as of yet. A very Tolkien vibe.
The city is pretty sweet if I say so myself. It's about three miles in diameter and is mapped on street level down to 2.5' equals a pixel. In part this is a result of the constraints of the computer I started it on. The under earth part is still loose, as I've been using it for as dungeon for different campaigns. So some parts are sketched in, others are detailed. The text varies as well. If I need something I spend time on it. I have no desire to make the six figures of NPCs that current estimates would require. That is just time wasting, better to make six hookers and use them, then worry about making five hundred.
The sandbox is about recognizing what can be faked and what needs to be theorized ahead of time, so you can do things on the fly. So I've bothered to sketch out the general powers of various religions, the priests are somewhat specialized by religion.