If you've enjoyed adventure module X2: Castle Amber (aka Chateau D'Ambreville), you've dabbled in the fantasy realm of Averoigne, whether you realized it or not! That adventure, in which in the PC heroes explore a strange, seemingly haunted mansion which acts as a sort of planar gateway into the world of Averoigne; a fantasy realm inspired by real world historical France.
I'll be honest here, I've not read a lot of CA Smith's work, and I can't speak authoritatively on his worlds. I include Averoigne in the Known World setting mainly because it is a canonical D&D offshoot setting in adventure module X2: Castle Amber. The adventure presents a stand alone quest for the PCs that is inspired heavily by the material it is based on, and Iecommend further research and reading to DMs who want to create further adventures in those worlds.
To learn more about CA Smith and his fantasy writings and worlds, check out the following sites:
http://www.eldritchdark.com/ Eldritch Dark - The Sanctum of Clark Ashton Smith
http://www.blackgate.com The Averoigne Chronicles at the Black Gate fantasy fiction site. There's a really cool little hex map here of the province of Averoigne that would work perfectly as an "area map" for X2: Castle Amber if you establish that at certain times, the "castle" manifests in the Known World, and at other times into the fantasy France inspired Averoigne "demiplane", similar in size and scope to the Thunder Rift setting for D&D.
