Ah, I missed that line. I was drawing on more traditional legends of Atlantis: a fallen civilization, far advanced in alchemy and technology for its time, that in its heyday conquered much of the Mediterranean, coastal Europe and North America. Perhaps we could edit the backstory to reflect the more traditional interpretation as seen in Timaeus and Critias? Shouldn't be difficult, as Atlantis is only mentioned in a single line in the setting description.

I have a few other ideas, though they're not quite as strongly formed. One is of a Sorcerer from Arabia wielding a grimoire of dark power (somewhere between legends of Irem and the Necronomicon for inspiration), or perhaps something drawing from Lovecraft in a more direct manner.