Originally I was asked to write a book called Stygia & Shem: Sands of Death. Later, this was changed to be two books, and the Stygia book was going to be titled Stygia: Sands of Death. Later it was renamed Stygia: Serpent of the South. I don't remember who made the name choices (generally, the titles are given to me and I have little input).
But, long story short, Stygia: Sands of Death is known to us all now as Stygia: Serpent of the South. Some of the adventures in the adventure book are quite old, and that one was written before or during my writing of Stygia.