A planet allied with Vulcan whose government asked for help against organised crime, leading the Vulcans to send surgically altered undercover agents, some of whom refused to return.
Agaron is a planet described in the Enterprise episode The Seventh. It is never seen on screen, but its history drives the story.
Years before Enterprise's mission, Agaron was plagued by criminal factions and corruption. At its government's request the Vulcan Ministry of Security sent a large number of operatives, surgically altered to pass as Agaronians, to break the smuggling networks from within. The operation worked, and relations between the two worlds improved.
When the agents were recalled, a number chose to stay and carry on the criminal lives they had adopted. A young T'Pol was among those sent to retrieve them. Her pursuit of Menos and Jossen ended with a death she later had removed from her memory at P'Jem.