What does the word watcher mean?

Usage examples for watcher

  1. " Aren't you rather forgetting the Watcher in the Dark? – A Woman Named Smith by Marie Conway Oemler
  2. In order to live the life of night, a watcher must not wake too much. – Essays by Alice Meynell
  3. He will be the Watcher of the Dead for a year and a day. – The Best Psychic Stories by Various