The first maps that were made by cartographers who sailed to Thras and lived to tell the tale show a group of sixteen islands, in a semicircle like a partially submerged coral atoll. Over the centuries other maps have been charted by spies and the number and size of the islands has varied, suggesting that the amphibious Sload have a volatile kingdom which fluctuates in land mass, either by the tides or some other, less natural means. The map above shows it as a small chain centered between Summerset, Yokuda, and Hammerfell. The largest of the islands, Agonio, seems the most stable, though later maps show it considerably larger than earlier maps.
They are buoyant creatures may move about with relative quickness and grace through an intricate network of coral formations and ancient shipwrecks.
The reach of Thras has been felt far beyond its own land. The Thrassian Plague which decimated Tamriel's population in the year 2260 of the First Era was their most outrageous attack against the mainland. When the Redguards came to Tamriel in 1E 808, they brought with them a tradition of burying their criminals on islands off their shore, to prevent their evil spirits from disturbing the living. The Sload took advantage of these graveyards of the coast, finding them suitable laboratories for their necromancy. The Redguards pushed back against the invaders, but reports of Sload living off the coast near settled lands from Stros M'kai to Abibon-Gora have surfaced well into the Third Era.
Recently the Sload have been quiet. Their hero, the King of Worms, Mannimarco, has likewise ceased to trouble Tamriel.