The Diana Tregarde series is a set of three urban fantasy novels by Creator/MercedesLackey. The primary character in all three is Diana herself, a romance novelist who is also a magical defender called a Guardian.

The novels in the series are:
* ''Burning Water'' (1989)
* ''Children of the Night'' (1990)
* ''Jinx High'' (1991)

''Burning Water'' is set in Dallas, where a serial killer is on the loose ... but he's not ''just'' a serial killer. Mark Valdez, a college friend of Diana's, is a Dallas cop in the Homicide division, and is picking up on hints that there's a mystic element to all the murders.

''Children of the Night'' is a prequel novel, set in New York City. A younger Diana meets some of the characters referred to in the first novel, and faces both vampires and her own fears.

''Jinx High'' is set after ''Burning Water''. Diana visits Jenks, Oklahoma [[note]]a suburb of Tulsa[[/note]], officially to run a writing seminar for an advanced English class at the local high school. Her real reason is to investigate a string of unusual events, that seem to be focused on the son of a close friend.

The anthology book ''Trio of Sorcery'' features "Arcanum 101". This book goes back to Diana Tregarde's college days, her first semester at Harvard. But of course she is a Guardian, and nothing is ever simple for a Guardian, not even what her neighbors are up to. This book came out in 2010 and contains numerous discrepancies in continuity with the books, such as the absence of several characters previously mentioned as having met Di in college.

'''The series contains examples of:'''

* AlphaBitch: Fay Harper from ''Jinx High''.
* ArtisticLicenseReligion: Lackey admits in the epilogue to ''Burning Water'' that she changed several elements of the Aztec myths she was working with for story purposes.
* BadassAdorable: Diana. Barely 5 feet tall and built like a ballerina, she's also a crack shot, holds a black belt in karate, and is a skilled magical combatant. At one point in ''Jinx High'', she takes out a much larger football player who is tripping on [=PCP=].
* BrokenBird: At some point before ''Children of the Night'', Diana was nearly killed by a magical being. Getting over that trauma is a major element in the novel.
* EmotionEater: Among the various types of "vampire" that appear in ''Children of the Night'' are this type. As long as they're feeding on positive emotions like the exhilaration of a concert crowd, they're fine. Once they begin feeding on pain and fear, however...
* TheEmpath: Diana.
* GrandTheftMe: [[spoiler: Fay Harper]] has been pulling this since before the American Revolution.
* HomeschooledKids: Fay complains at one point about having to waste her time going to high school instead of being homeschooled by a private tutor [[spoiler:at least, that would have been what she was ''officially'' doing ...]]. Oklahoma law would have allowed Fay to be homeschooled, Lackey never explains why Fay's mom didn't set this up [[spoiler:before moving herself into Fay's body]].
* HumanSacrifice: The murders in ''Burning Water''.
** Some of the deaths in ''Jinx High'' probably count as well.
* LaserGuidedAmnesia: A mystic trap set up by Tezcatlipoca in ''Burning Water'' works similarly to this trope. Once Diana trips it, she retains all her knowledge, but can't put things together to solve the case unless someone else points out a connection.
* MindControl: How Tezcatlipoca [[spoiler: in Robert's body]] gets Sherry to prepare to be sacrificed.
* MistakenForCheating: Deke decides in ''Jinx High'' that Diana and his dad Larry are spending time alone together because they're carrying on an affair. The real reason is to hunt down the mystical danger that wants Deke for lunch. But Deke doesn't find out about his ''own'' mystic talents until late in the novel, and had no clue that both his parents were in Diana's Scooby Squad in college, so you can't really blame him.
* MostWritersAreWriters: Diana pays the bills with cheesy romance novels.
* MRSDegree: Fay muses at one point in ''Jinx High'' that half her female classmates are only going to college to snag a husband.
* MuggingTheMonster: In ''Children of the Night'', a shapeshifting souleater vampire who leaves the villains' group and comes back sated is said by the group's leader to have been "trolling for rapists" in the form of an attractive young woman. Dave, who is repulsed and uncomfortable about basically murdering random people but needs to feed, thinks this sounds like a good idea, and so he wanders Central Park until a junkie attacks him. It doesn't turn out to be the guilt-free experience he hoped for, however.
* OneHourWorkWeek: Specifically averted by Diana during the writing seminar in ''Jinx High''.
* OurVampiresAreDifferent: ''Children of the Night'' features three different kinds of supernatural creature which can loosely be considered vampires.