Talon Karrde is a human male who runs one of the largest independent smuggling and information-brokering organisations in the galaxy. He was created by Timothy Zahn and introduced in Heir to the Empire (Bantam Spectra, 1991). His homeworld has never been established.
The third faction
Karrde's function in the Thrawn trilogy is structural and clever: he is neither Empire nor New Republic, and he intends to stay that way. He deals in information, he keeps his organisation out of other people's wars, and the plot repeatedly punishes him for believing that neutrality is available. Watching a professional get dragged into a conflict against his own commercial judgement is a better engine than most Star Wars antagonism.
An organisation, not a gang
Zahn writes the smuggling trade as a business with logistics, personnel problems and a reputation to protect — a notable contrast to the vaguely piratical treatment it usually gets. Karrde's lieutenants, Mara Jade among them, are staff. His vornskr pets are the only whimsical thing about him.
Legends only
Karrde belongs entirely to Star Wars Legends. Current canon has smuggler-broker figures who occupy something like his niche, but he himself has never been carried across.
Reading note
He is the reason the Thrawn trilogy feels like it takes place in an economy, and the reason the New Republic era reads like a place with jobs in it. If you like that, the later Zahn novels keep him around and keep him useful.
