- “I've been indexing the Watcher Diaries covering the past two centuries. You'd be amazed at how numbingly long-winded some of these Watchers were.”
- ―Rupert Giles[src]
Watchers Diaries were a collection of journals, logs, and diaries kept by Watchers throughout the centuries, written with the intent to be used in research for following Watchers. The main focus of the Diaries were the actions of the Slayer, including as well historical records on demons and vampires — but not always precise nor complete.
- “My death would already leave far too many important matters at loose ends. That is one of the unspoken purposes of the Watcher's Files. So that, when the end comes for me, others might have the information they need to take up the burden. May God have mercy on their souls.”
- ―from the journal of Rupert Giles[src]
In 1997, the Watcher Rupert Giles researched about the vampire Angel, but there was nothing under this name in text, except a Watcher Diary with entry from 200 years before, with a mention in Ireland of Angelus. It described him as the one with angelic face, with a tattoo behind his right shoulder. According to the diary, he left Ireland and wreak havoc in Europe for several decades; until about the year 1920, when he went to America, shunned other vampires, and lived alone, with no record of hunting.
In his research on Spike, under the name William the Bloody, Giles read that the vampire had earned his nickname by torturing his victims with railroad spikes. Notably, the Watcher also discovered Spike had fought two Slayers in the last century, and killed them both. Although, his age described as barely 200 was imprecise, as William was born in 1853 and sired in 1880. Another incorrect information was about his paramour Drusilla, reported as killed by a mob in Prague.
In the same year, Slayer Buffy Summers and her friend Willow Rosenberg stole a Watcher Diary from Giles to study Angel. The two girls found an entry with an illustration of a noblewoman from 1774, which inspired Buffy's Halloween costume.
Also in 1997, Giles was indexing the Watchers Diaries covering the last couple of centuries. He noted the "numbingly pompous and long-winded" personality of some of the past Watchers. In 1999, Buffy Summers' new Watcher, Wesley Wyndam-Pryce, attempted to begin his writings on the Slayer, asking her to describe her patrol from the previous night. Wesley then had the opportunity to read Giles' first entry on Buffy, which described: "Slayer is willful and insolent. Her abuse of the English language is such that I understand only every other sentence."
In 2000, Buffy suffered a near-fatal encounter with a vampire, and studied the Watchers Diaries to learn more about previous Slayers' deaths and how to avoid making the same mistakes. However, she found the journals lacking any details about these deaths, which Giles speculated to be because the Watchers found it too painful to write about. In their research, they found the description of a Slayer in early 18th century who had forged her own weapons.
In 2001, Dawn Summers and Spike broke in into the Magic Box shop to find Giles's hidden notes. Reading one of the books, Spike noted Giles wrote in a small handwriting, and "as dull as he talks." With the information Giles had secretly archived, they discovered Dawn's original identity as The Key.
Following the Twilight crisis and Giles' death, Faith Lehane inhered most of his possessions, which included his Watchers Diaries collection. With Angel, they used his diaries to deal with Giles' unfinished business and as a guide to fight demons, such as a Plagiarus demon in his late years. The collection of Diaries pointed out to Alasdair Coames as a go-to guy in demon biology, and Giles' journal described his own traumatic encounter with the Highgate Vampire. Ultimately, Angel and Faith had the intention of studying the files to learn how to resurrect him.
In the 23rd century, Slayer Melaka Fray found out an abandoned apartment full of past Watchers Diaries, with an illustration of the Mʔ weapon on its floor. Reading through the old journals, she was able to learn about and connect with her predecessors, as she neither had the Slayer dreams nor a Watcher to guide her.
Although, when time-traveled into this future, Buffy did not found useful information, only "a few sketchy references that might be me, or my friends," and the books did not even mention the existence of thousands of activated Slayers. The Watchers Diaries mentioned a certain "Gates", the last great Watcher, who sacrificed himself at "the Battle of Starbucks". The inconsistencies of these writings may indicate that this was a reference to Giles' death in a battle in Sunnydale.
After assisting the Scooby Gang in the Reckoning, Melaka returned to the 23rd century, although a new and improved timeline. A group of Slayers welcomed her and explained that the Watchers Diaries described how she and her allies saved the world, which helped the Slayers forge a much better future than the one she came from.
Behind the scenes
- In "What's My Line? Part One", Giles announces to be "indexing the Watchers Diaries covering the last couple of centuries," with piles of at least a hundred books; while in "Bad Girls", Wesley confirms with Giles if the less than fifteen books were "all the Diaries, including [Giles's] own." The difference in quantity may be a continuity error, but various in-world causes are plausible, such as the loss of books from the library in "Gingerbread", or Giles' distrust on the new Watcher making him hide most of his collection, or even that Wesley had asked him for the totality of Diaries only under a specific theme.