The Zhentarim—also known as the Black Network—is a loose affiliation of merchants, mercenaries, and malefactors. Common folk know the Zhentarim as the people to talk to when you need the best guards or mercenaries money can buy. And if the cargo is shady or the cause you’re fighting for is questionable or even unjust, the Zhentarim don’t mind.
Affiliation with the Zhentarim can be profitable to sellswords, thieves, and rogues of every stripe. It’s plausible that adventurers might become members of the organization—but like most residents of Faerûn, they won’t know the full extent of the Zhentarim’s operations and goals. A member of the Zhentarim thinks of himself or herself as a member of a very large family and relies on the Black Network for resources and security. However, members are granted enough autonomy to pursue their own interests and gain some measure of personal power or influence.