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.

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!!The series contains examples of:

* ActuallyRealMagic: This trope is how Diana and Mark originally met (the scene is a flashback in ''Burning Water''). During their college days, one of Mark's buddies was studying anthropology, and organized a Halloween seance to see if there might be something to those old rituals. They were trying to summon Julius Caesar and got a demon instead. Diana had to put studying for her mid-terms aside to rescue Mark.
* AkashicRecords: In ''Burning Water'', Diana uses her associate, who is by nature a medium, to access the akashic record to get information about the ancient history behind the threat they're facing.
* AlphaBitch: Fay Harper from ''Jinx High'' is the Alpha Bitch from hell: she's actually a two-hundred-year old, bodysnatching witch who enforces her will with mental control and fatal "accidents".
* ArtisticLicenseGeography: In ''Burning Water'', a sacrificial victim is found on a rock at Bachman Lake Park in Dallas, Texas. Diana is examining the crime scene with a local police detective. Their conversation is pretty standard for the genre--bloodstains, time of death, witnesses, &c. What's missing from their exchange are the times when they would be unable to hear each other due to the jet airliners landing at and taking off every five minutes from the adjacent Love Field airport.
* 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.
* AssholeVictim: Most of the murder victims who get any introduction in ''Burning Water''.
* 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=].
* BadPowersGoodPeople: ''Children of the Night'' had a band member become a psivamp, someone who feeds off of the emotional energies of others and can affect emotional states to get the right intensity. This generally leads to either burning the victim out or giving him or her a fatal heart attack. As a psivamp weaned off of positive emotions and adjusted to fear and rage, he can't survive on food anymore. He eventually decides not to go along with his other psivamp bandmates and the vampire dad and has a fantasy of feeding only on the deserving, so he goes out and kills first a crackhead trying to kill him, then a pair of almost-rapists, before he realizes that the hunger doesn't distinguish between the bad guys and the victims, and he knows he'll slip. In the end, [[spoiler:he helps take out the other psivamps, then commits suicide]].
* BondageIsBad: The German porn shop owner in ''Burning Water'', who at least shows very real callousness when he didn't check that a sub had a rubber/latex allergy and caused her death from anaphylactic shock.
* BoundAndGagged: In ''Burning Water'', one minor character realizes he's been targeted by a mind control spell and demands his brother (a cop, so he actually has handcuffs available) and his sister-in-law cuff him to the bed. It holds him long enough for two other characters to break the spell.
* 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: In ''Children of the Night'', Di Tregarde refuses the call to use her Guardianship, and ignores an inept sorcerer's plans to summon an inhuman demon that was too strong for him, thinking it's not her problem. Naturally he summoned the thing, it killed him and was wounded in the process, and it then went after Di, because even if she wasn't doing anything with it Guardianship sticks around. She beat it, but the panic attacks triggered by anything that reminded her of it lingered, as did the lesson that ignoring these things, on a purely selfish level, meant that they would meet her on their terms.
* CannotCrossRunningWater: ''Children of the Night'' addresses this matter by saying that vampires don't cross running water because they're territorial and streams often serve as natural boundaries for hunting territory, with the vampire dryly adding that one might as well say vampires can't cross major highways.
* CatsAreMagic: Subverted in the short story "Arcanum 101". When Di is observing the house of someone she believes may be involved in black magic, she sees a cat wander past the house with no reaction... and thinks to herself that this doesn't mean anything because, superstitions notwithstanding, cats are too self-absorbed to notice magic that isn't affecting them directly.
* CharacterOverlap: in ''Jinx High'', Tannim from the ''[=SERRAted=] Edge'' series shows up as a student at Jenks High School. He has the nerve to get Diana on the dance floor -- and in his own novel ''Chrome Circle'' he refers to witnessing Diana and [[spoiler:Faye's]] knock-down magical fight in the school parking lot. It was the trigger for Tannim getting 'serious about magic... or else it was going to have me for lunch.'
* ChristianityIsCatholic: Lampshaded in ''Jinx High'', in which a character pursued by demons considers sheltering in a nearby church, because in movies demons can't set foot on holy ground. She decides against it because the movies always show Catholic churches and this one is Methodist.
* CompulsorySchoolAge: Starts out justified in ''Jinx High''. The villain GrandTheftMe'd her daughter, who was already in public school. Then the justification falls apart when she thinks about how previously she'd been able to claim her current body was being educated at home by private tutors -- homeschooling is legal in Oklahoma.
* CrazyPrepared: Despite her increasing recklessness during ''Jinx High'', [[spoiler: Fay Harper]] the villian, is this. [[spoiler: continual GrandTheftMe or not, it's the only reason she's lived this long.]]
* 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.
* DemonicPossession: The BigBad of ''Jinx High'' tries crossing this trope with SoulJar -- the plan is to summon three demons and bind them into the electric guitars used by the band playing at Spring Prom. The demons are under orders to pump as much negative energy as possible into the music, triggering a riot (and giving said villain far more blood magic energies than were spent for the summoning). [[spoiler:Unfortunately, one of those guitars was ''already'' occupied by a spirit that wanted nothing to do with this, thank you. Diana and the "good" guitar manage to fry the other guitars and send the demons back to Hell.]]
* DomesticAbuse: In ''Burning Water'', there's a scene where a patrol cop is telling the waitress at a diner (who volunteers at a domestic abuse support group) about recent domestic violence cases he's responded to so that she can contact the victims and get them help before things get out of hand.
* DontWakeTheSleeper: In ''Jinx High'', there's something dangerous sleeping under Tulsa, Oklahoma.
* 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.
* FamilialBodySnatcher: The villain of ''Jinx High'' has survived since before the American Revolution via GrandTheftMe, but can only possess a blood descendant. [[spoiler:Or at least a blood relative. The end of the novel strongly implies she was able to jump back to the current host's mother, a previous host body.]] She's tried moving into the bodies of non-relatives, and they've all died.
* FeedbackRule: During the Spring Prom in ''Jinx High'', almost everybody on stage has trouble with feedback in the sound system. A building [[note]]and magically-aggravated[[/note]] storm is causing a huge buildup of static electricity, so possibly justified if no one at the school has ever heard of surge protectors.
* ForHalloweenIAmGoingAsMyself: Invoked and averted in the story "Satanic, Versus..." The heroine considers going to a costume party with her boyfriend as a witch and a vampire--but he argues that there's no point in going as what they really are, and they dress as Series/TheAvengers instead.
* FriendlyNeighborhoodVampire: Andre. When Diana first encounters him in ''Children of the Night'', she thrusts a crucifix in his face. His response is to look at her sadly, take the cross from her hand and kiss it reverently. He and Diana become allies and lovers as the story progresses.
* GasStationOfDoom: The opening scene of ''Jinx High'' has a character walking to a closed gas station to use the pay phone (the book was written before everyone and his goldfish had a cell) and promptly becoming Eldrich Horror Chow.
* 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]]
* GiveMeBackMyWallet: In ''Children of the Night'', Diana Tregarde doesn't have the energy to confront a pickpocket, since all he got was a decoy wallet filled with newspaper.
* GrandTheftMe: [[spoiler: Fay Harper]] has been pulling this since before the American Revolution. [[spoiler: What makes it even more horrible is that she can only do it to ''her own child''. Fay's been an almost literal Black Widow for centuries; marrying for wealth and breeding stock, killing her husband, then effectively killing her children - or in the real Fay's case, keeping her locked up in an asylum, just in case.]]
* HolyBurnsEvil: Subverted in ''Children of the Night'', when Diana first encounters the vampire Andre. She thrusts a crucifix into his face; he reacts by gently taking the crucifix from her hand and kissing it, saying, "I need not fear the Son of God, only the sun in the sky." Fortunately for Diana, Andre is a FriendlyNeighborhoodVampire.
* 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]].
** ''Jinx High'' was written in the early nineties. Maybe the law was different, then? Or maybe Fay was complaining about the social constraints rather than the legal ones - [[spoiler: she definitely didn't want anyone thinking of the rich, 'orphaned' homeschooled girl being so weird they came to check on her on a regular basis. Going to high school may be boring, but as long as she keeps up the facade it's probably by far the safest option (not to mention all the Power she could skim off the seething hormonal dramas of hundreds of teens penned up together for 30-odd hours every week)]]. ...Or maybe Lackey just ignored that fact because she needed Fay in high school in order to cross paths with Diana.
* HorrorHunger: ''Children of the Night'' has an Unwillingly Evil character who has been converted into a psivamp; he can only survive by empathically causing and feeding on strong negative emotions, rage and fear etc, in people. He can't control it very well, so they either die or "burn out", which is implied to be worse. The hunger is described as being ravenous and directly connected to his empathic ability, and even when he feeds it it's never really quiet. He tries to feed only on the attack junkies and rapists of New York, preying on the predators, but the hunger doesn't distinguish between these people and their victims, and he knows he won't be able to do this for long before he loses control.
* HumanSacrifice:
** The "Texas Ripper" murders in ''Burning Water'' (thought to be the work of an ordinary serial killer by the cops) are actually a series of sacrifices to the Aztec gods.
** Some of the deaths in ''Jinx High'' probably count as well.
* ImpossiblyLowNeckline: In ''Jinx High'', the villainess commissions a costume straight out of the American Revolutionary period for the school dance. The bodice is cut so low that one of her boyfriends has almost complete access to her boobs while she's wearing it (handy when you need to distract said boyfriend while the mind control spell takes effect).
* IntoxicationEnsues: A dark example in ''Jinx High'', when magic is used to shoot [[http://en.wikipedia.org/wiki/Phencyclidine PCP]] directly into Sandy's bloodstream.
* IOweYouMyLife: In ''Children of the Night'', Diana rescues several kidnapped UsefulNotes/{{Romani}} children. The clan considers themselves to have an honor debt to Diana until she finally finds something they can do to clear the debt in ''Burning Water''.
* ItsAllAboutMe: The BigBad of ''Jinx High'' understands the magical law of karma ... specifically she understands that when others do wrong, it leaves them open for her to harm them. The idea that she might be subject to this same law doesn't even occur to her.
* KickingAssInAllHerFinery: At one point in ''Jinx High'', Diana Tregarde takes on a much larger jock, who happens to be high on PCP, while wearing a silk formal dress. As the dress was specifically designed with a full enough skirt to allow karate kicks, and she was combining the karate with her psychic powers, the dress survived undamaged.
* 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.
* LifeEnergy: ''Children of the Night'' has 'psi-vamps' who drain energy from others. In this case the energy is tied to emotions -- they drain excitement at first, and later hate and fear. Also, a completely drained victim is usually not physically dead, but is emotionally/mentally burned out (described as a mindless hulk, with no chance of recovery).
* {{Magick}}: In one of the novels, Diana comments on how pretentious a foe who insists on spelling magic with a k is.
* 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.
* MustBeInvited: Andre Le Brel, in ''Children of the Night'', can enter public buildings freely but cannot enter Diana's apartment building (not just her apartment) until invited to come in. Once the invitation is given, though, he can break in at a later time to take shelter from the sun.
* 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".
* OccultDetective: Diana Tregarde isn't officially a detective, but a Guardian's job description includes finding out whether the Bad Stuff Going On is mystical, and ending it if it is.
* 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.
* ThePowerOfRock: ''Jinx High'' contains a magirock battle between two demon-infested electric guitars supported by a dark sorceress and a hippie-infested guitar and a guardian/witch. It ends when the speakers, not intended for arcane use, explode.
* PredatorTurnedProtector: Alluded to in ''Children of the Night''. One of the psivamps has been fighting his need to feed, and the others realize once he heads back to their base that he's given in. He tells them a folk tale about a lion cub adopted by a herd of sheep, who grew up thinking he was a sheep until the day a pack of wolves attacked the flock. The others figure he's gone over to their side, he doesn't bother telling them that the story ends with the lion killing all the wolves. (He'd chowed down on a couple rapists so he could act as TheMole.)
* RefusalOfTheCall: Di tried this for a while in the past, with [[TheCallKnowsWhereYouLive traumatic consequences]].
* SamaritanSyndrome: Diana has a minor, slightly selfish version of the trope in ''Children of the Night''. She's a Guardian, endowed with incredible mystic powers, and she has to help anyone in her area who really needs those powers. If she doesn't, there are other Guardians who will try and stop a developing crisis, but they're a little ways away and one of them is old, one of them has a broken leg, and one has extreme acrophobia. They'll do it, but she doesn't want them to have to, not when her only problem is that the threat in question gives her panic attacks.
* ScrewTheRulesIHaveSupernaturalPowers: In ''Jinx High'', a VainSorceress uses her magical powers to rule the local high school.
* SexMagic: In ''Jinx High'', the BigBad can (and does) use other forms of magic, but seems to prefer sex magic when it comes to controlling people.
* SinInvitesPossession: The villain of ''Jinx High'' can't GrandTheftMe the next generation until that person can be morally corrupted.
* StandInParents: In ''Jinx High'', the villain [[spoiler:who {{Body Surf}}s to her daughter each generation]] appears to be under 18, and has an artificial construct that masquerades as her aunt/guardian while her mother is in a mental hospital [[spoiler:with the personality of the daughter just evicted from her original body in Mom's body]].
* ThrowingYourSwordAlwaysWorks: It's lampshaded in ''Burning Water'' when Mark Valdez remembers how he met Diana Tregarde for the first time.
* 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.
* VirginSacrifice: Inverted in ''Burning Water'', where Tezcatlipoca needed to sacrifice a woman who had borne at least one child to return to Earth.
* 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.
* YourVampiresSuck: In ''Children of the Night'', vampire Andre dismisses several traditional limitations as "silliness," in particular the inability to cross running water, which he ascribes to a misunderstanding of their tendency to set territorial boundaries. He tells Diana that it could just as easily be said that they do not cross mountain ranges or major highways, since they define their territories by major landmarks.
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