This is inspired by an old ENWorld post I ran across: “Is Dark Sun an alternate future Forgotten Realms?” Now, I’m not interested in whether that was in the designer’s minds, or whether that notion is supported by canon; fairly clearly the answer to both questions is No. However, the original Dark Sun Boxed Set implies that Athas was once much like other D&D worlds, until Defiling magic came along and messed things up. Later lore mostly contradicted that notion, but that was the version of Athas I fell in love with, and that’s how it is in my campaigns.
Now I find myself running Forgotten Realms (don’t ask why; it’s a long story). I apparently have a deep aversion to playing standard D&D settings stock; I always heavily modify them in some way (I once turned Greyhawk into Middle Earth, for instance). So I was looking for some angle to make the setting my own, and came upon the idea of making the Forgotten Realms setting into my version of Green Age Athas.
The problem, however, is that, while I am somewhat knowledgeable on Dark Sun lore, I know almost nothing about Forgotten Realms. Perhaps this would be better asked in a Forgotten Realms forum, but I was hoping for some ideas and tips on how this could be accomplished; how the lore of FR could be shoehorned into the backstory for Athas. So—tips? Thoughts? Ideas? Thanks!