I've been working on a homebrew D&D setting for three years. It doesn't seem like that long when you think about how long some of those boxed sets have been around, but its been a long time for me. You see, I've changed settings and games so often in my past that it's been hard for my friends to keep up. More often than not I'm the GM, because that's what I like to do. So I'm sure it can get kind of hectic when a genre book pulls me in and suddenly we have to stop pretending to be warriors and everyone is a spaceman.
Except, over the last few years, that hasn't happened. AD&D has always been the mother of all roleplaying games for me. No matter who or what I dallied with, I always returned to her. It was a fit of pique that led me to design this latest setting, and somehow it has grown like a weed, spreading in all directions and consuming my desire for other games. I wanted to introduce AD&D to someone who'd never played it before; she joined our online gaming group (too far apart to play at a table any longer, sadly) and we were going to start out with some Planescape, the collective favorite. Except, she had no grounding in what a D&D game was supposed to be like, so all the Planescape meta-verse stuff just went right over her head.
"Alright," I said, "I'm just going to have to design a generic D&D world for us to play in for a while."
As a basis I took my memories of the first setting I'd ever really run, changed them to suit my new (more mature I hope) outlook on life, and advanced the setting about eight hundred years or so. The 8th Age, the campaign of my highschool years, became the 10th Age, and I've been working on it ever since. All throughout graduate school and my year teaching English in China. This is the fourth year after its inception and I have not played any other roleplaying game for more than two or three sessions. When we play D&D it is always either in a TSR setting, or in the 10th Age. It just keeps growing.
So, what are the design goals I had when making the 10th Age? The first was to encapsulate that archetypical D&D feeling. You know what I mean: ruins, mystery, adventure, adventuring companies. But, as I've always been a sucker for verisimilitude, I wanted to not all get all that good stuff in there but also to extrapolate what it would actually be like in such a place. Strip away the romance of D&D (which has come to encompass its later editions to such an extent that it seems that the romance has really consumed the realism on every level) and decide what a magical society would look like.
Real historical theory went into the developing histories of the 10th Age. Ethnographic information, nationbuilding, and linguistic theory all went into the melting pot. What came out has a lot in common with the Forgotten Realms because that was my favorite TSR boxed setting as a young man, but I like to think there are other things happening in the world of Atva-Arunë that make it unique.
My design goal has always been to have a post-modern D&D setting, not in the Planescape sense where everything is mutable, but in the sense that the old tropes are no longer standing alone but rather have been analyzed and integrated into the setting on a deeper and more meaningful level. One of my favorite elements from Greyhawk and FR was the acknowledgement of adventurers as a force in the world, and this was key to my original formulation of the setting. Adventurers exist! Adventuring companies are chartered, they explore ruins, people know about them. In the 10th Age they're a combination of grave robbers, rockstars, and Hollywood celebrities.
As I wrote the other day, I am working on an approachable Player's Guide to the setting so that people can get into it without slogging through all the unnecessary stuff that I've added along the sidelines to make the setting fuller. If, however, you are interested in checking out what exists (it is just an undifferentiated mass of information, so beware!), feel free to.