The Sea of Merchants is the open water between the western coast of the Tarkhon Empire and the eastern edge of the Western Isles. Its eastern shore is the Neferati Kingdoms of Fire, Kabir and Yaif among them, whose harbors face it directly. Its western shore is the archipelago: Sheîr's mainland strip, the islands of Istokos, and past them the long disordered scatter of the Shattered Sea. The Western Isles treats this water as its eastern boundary and ends where it begins.
The name is literal, and it is earned at the eastern end of a single road. A cargo moving from the Middle Sea to the Shattered Sea has no other way to come. It clears the Tarkhon Strait, the only sea gate out of the inner sea, pays the empire at the narrows, and emerges here with the western islands in front of it. The Sea of Merchants is the threshold the corridor crosses. It is also where the second and third hands reach for a purse Tarkhon has already opened.
A hull that has paid the empire is not finished paying. Sheîr holds the eastern lip of the archipelago and sells the pilots and charts a stranger needs to thread the islands, and charges a toll for the approach besides. North of Sheîr the route bends into Phyndarr Sound, where Tollgate has taxed every passage for three centuries from its fortress at the Sound's mouth. Three powers tax one flow of goods across this water, and none of them answers to the other two.
Out of Camaran with a full hold of oil, and I paid the strait, paid the Sheîr pilot, and paid the Gatemaster before I had sold a single jar. A man starts to wonder who the oil belongs to. — a Camaran oil-captain, recorded at Teku