Secret agents placed on developing worlds to watch over individuals important to the future, among them Tallinn, who guarded Renée Picard in 2024 on behalf of the Travelers.
The Supervisors are operatives who live unnoticed among a population and protect a single person or event on which the proper course of history depends. They carry advanced tools, including transporters that work through a kind of vapour.
The second season of Star Trek: Picard introduces Tallinn, a Romulan who has spent years watching over the astronaut Renée Picard ahead of the Europa Mission. She helps Jean-Luc Picard's crew against Q and Adam Soong, and gives her life in Farewell so that Renée can fly.
In the same episode Wesley Crusher appears and tells Kore Soong that he and his fellow Travelers are the ones who send out the Supervisors. The idea builds on Gary Seven, the mysterious agent of the Original Series episode Assignment: Earth.