Lankhmar, for those of you who are sure you know the name from somewhere, but not quite from where, is the largest city in the world of Nehwon, and the setting for about half of Fritz Leiber’s brilliant Fafhrd and the Gray Mouser stories. But that’s as much of a clue as you get 🙂
In one particular story, “The Wrong Branch“, the Mouser and Fafhrd visit what is recognizably a version of historical Earth. This is achieved through the magicks of Ningauble of the Seven Eyes, but here’s thing: old Ning doesn’t seem to have that level of power in any other story of his. So I don’t think he actually used his own power at all, or at least that much. I think he hitched a ride for our heroes on the back of the Banestorm.
Now, it’s obvious that there’s no direct connection between Nehwon and Yrth. It’s highly unlikely that they exist on the same world, for example (indeed, as theorised by the Gray Mouser, Nehwon’s cosmology is damned peculiar). But if travel between the two worlds is possible, than travel will no doubt occur. Indeed, the true forms of Ningauble and his fellow sorcerer Sheelba are never seen – could they be Djinn? It would explain a lot, in addition to giving a plausible way to connect the two worlds.
Now, Nehwon is a world of much more casual magic use than Yrth, but in most other respects the two are fairly similar. There are gods of Lankhmar (and also the Gods in Lankhmar), but these (with the exception of Death) could fairly easily be explained away as demons or liches. Crossing over the two is best done, I think, by letting some of the flavour of Nehwon leak into Yrth. The staid medievalism of Yrth could stand to be weirdened up a bit, with more mystery, more monsters and more magicks. Making it a more lawless and dangerous world only increases the possibilities for adventure.
But leave Tredoy just the way it is – it’s already perfectly Nehwonian in its own wonderfully strange way 🙂