Watcher

A Watcher is a person who watches. This term is used in several continua, notably Buffy the Vampire Slayer and Highlander, for groups of people that, for different reasons, want to keep tabs on people with special talents (Slayers and immortals, respectively). The existence of Watchers in both continua occasionally leads to crossovers between the two, with varying degrees of success.

Not to be confused with the Watcher in the Water of Middle-earth.