The leading Megacorp of the Atlantic Federation
If one travels, you might notice it. Each one has a blue orb on their signage or somewhere in the shop. The merchants seem to specialize in foreign goods, but often buy local produce and products, to trade in other places. They seem totally unrelated to the others. It seems to be a secret organization, but nobody knows for sure.
There is a person who has a well-known reputation, probably involving something illegal. But this person is either very clever and crafty, or really like his or her privacy, for no one knows who this person actually is. As an added twist, perhaps this person is of an age that would noramlly be wildly inappropriate (say, a child is a much-feared bandit) or maybe not the expected gender or even race.