Mercantilism is the ability to judge trade goods — quality, provenance, what they will actually fetch — together with the working knowledge of routes, markets and the people who control both. Real merchants specialise, in cloth or metalware or pottery, but at introductory levels the skill applies broadly across whatever a character’s own culture trades in. Foreign markets carry the same distance penalties as foreign folklore, and a merchant a long way from home is regularly relieved of money by people who know the local price.
Where a campaign uses trade specialisations, they are named for the Lore or Craft skill whose commodities they cover:
| Agriculture | Herblore | Mineralogy |
| Animalcraft | Hideworking | Perfumery |
| Brewing | Jewelcraft | Shipwright |
| Ceramics | Lockcraft | Textilecraft |
| Fishing | Masonry | Timbercraft |
| Fletching | Metalcraft | Weaponcraft |
| Glassworking | Milling | Woodworking |
Market Size. Urban settlements carry a Market Size from 1 to 9 — a composite of population, position on trade routes and geography — and it governs what can be bought, what can be sold and at what depth. It is not simply a measure of size: a modest port astride the right sea lane outweighs a larger inland town, and the greatest markets are almost always harbours.
Merchant fleets sail seasonally to fixed destinations, and a single such convoy may be worth more to both ends of its route than a year of overland traffic. Knowing when one is expected, and what it will be carrying, is worth as much as knowing the price.
Accounts are arithmetic, and a merchant with no Mathematics is at the mercy of whoever keeps their books.