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.
* TheCallKnowsWhereYouLive: Di was not enthusiastic about become a Guardian, and tried to ignore her magical heritage in favor of a normal life. Unfortunately, a Guardian's power - especially if untrained and going unused - is a beacon to all kinds of supernatural nastiness, and Di's attempted RefusalOfTheCall nearly got her killed when a particularly dangerous specimen tried to have her for lunch.
* EatingOptional: Andre only gains nourishment from blood, but can drink and enjoy other liquids. The psivamps from ''Children of the Night'' become this as well.
* 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.
* GettingCrapPastTheRadar: An in-universe example in ''Jinx High'': the spring dance at the high school starts off with a Maypole dance, and Diana recognizes the specific form of the dance as the Sex Magick variant instead of the "standard" fertility rite (which would be bad enough in the [[TheFundamentalist Bible Belt]]). [[note]]The Maypole=fertility rite is questioned in RealLife, but within the novel it's established fact.[[/note]]
* 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.
* IntoxicationEnsues: A dark example in ''Jinx High'', when magic is used to shoot [[ PCP]] directly into Sandy's bloodstream.
* KissOfTheVampire: [[OurVampiresAreDifferent "Standard" vampires]] like Andre have this ability, Diana theorizes it developed as a way to keep dinner from running away. When conscious, the vampire can control the amount of pleasure the other person feels. When Diana nicks her wrist and sticks the cut into an unconscious [[note]]and severely injured, which is why she's trying this[[/note]] Andre's mouth, let's just say it gets a bit out of control.
* 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.
* MagneticMedium: Mark Valdez ''would'' be one of these if he wasn't under heavy shielding -- it's very easy for spirits to slip into his body. [[spoiler: Robert from ''Burning Water'' is another one, who's become a WillingChanneler for Tezcatlipoca.]]
* 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.
* NoWarrantNoProblem: In ''Jinx High'', when Diana, Larry, and Mark find [[spoiler:Fay Harper's]] ritual space, Mark picks the lock on both the gate across the road and the building itself.
--> '''Mark:''' Boy, I'll tell you, it's amazing how careless people are, leaving their gates unlocked like that.
** Justified in that while Mark's a cop (outside his jurisdiction, but still a cop), it's not like anything will be going before a judge the group just wants to sabotage any spells the owner has prepared and drain off the owner's stored {{Mana}}. And the owner can't call the cops about the break-in either, without causing serious issues for [[spoiler:herself]].
* NudeNatureDance: Alluded to in ''Children of the Night'', when Diana tells another Wiccan to bring his robe to the Samhain ritual because "I don't do skyclad".
* 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:
** Conventional undead vampires like Andre [=LeBrel=], who follow a lot (though by no means all) of the traditional folklore. In particular, they're vulnerable to sunlight and wood (thus the whole bit about stakes) but not garlic, can cross running water with no difficulty (Andre suggests the superstition about this came from the tendency of vampires to be territorial and streams and rivers making excellent natural boundary markers), and do not sleep in coffins but do need to have a small amount of the dirt from their grave site with them when they rest (Andre keeps his safely stored inside a metal armband, ensuring that nobody will be able to separate him from it without taking off his hand).
** {{Emotion Eater}}s like Master Jeffries, who can turn normal humans like Dave and his bandmates into more of his kind by an unclear process involving dubious red pills. Not everyone is capable of making the transition, however - Jack, the drummer, only gets a temporary high, and around eight other people die from whatever it is Jeffries gave them. They start off feeding on positive emotions, but being fed the pain and terror of a human being's death alters their metabolism such that afterward they can only take sustenance from negative emotions.
** A Japanese ''gaki'' or "hungry ghost," depicted as supernatural beings who feed on any number of things. Many ''gaki'' feed on harmless things, but Di describes nastier varieties that feed on flesh, blood, or souls.
* RefusalOfTheCall: Di tried this for a while in the past, with [[TheCallKnowsWhereYouLive traumatic consequences]].
* VaginaDentata: [[spoiler:Fay Harper's]] Servitor (a type of magical construct) was deliberately built with one of these, and it's how the Servitor feeds. Makes for a rather [[{{Squick}} squicky]] end for one character, even if he ''is'' a classic JerkJock.
* YourSoulIsMine: Hidoro in ''Children of the Night'' is a soul-eating ''gaki''. Like most of its kind, it takes extra enjoyment from making the deaths of its victims as painful and terrifying as possible, and can shapeshift into its victims after eating them.