The Vein
From ThornsWiki
The Vein is the most prominent trade route in the world. It runs primarily through Mugroba and into Anaxas, and has channels that travel to Hesse, Bastia and Gior via their coastlines and rivers. It is controlled by Silas Hawke and the Bad Brothers, who do the majority of negotiation and make the Vein run smoothly.
The Vein deals in all manner of trade goods - on the legal side, grains, textiles, spices and machinery; on the not-so-legal side, drugs, and illegal weaponry. Prices are all set by the standards of Silas Hawke, and two types of currency are used: overworld currency (the moneys of the various kingdoms that the Vein travels through) and underworld currency, which is used for procuring illegal items. Strangely enough, though it can be used in far fewer places than overworld currency, underworld currency is more valued and sought-after on the Vein (probably because it can be used to buy security and loyalty in ways that overworld currency cannot).
Currently, competition to the Vein is cropping up in Old Rose (The Drain), though Silas Hawke is doing anything in his power to quash it before it takes hold.