Acceptable Breaks from Reality: Even if Mosely is implied to bend the rules for Gabriel since they are friends, and the police force knows Gabriel is doing research for his books, if Mosely acted this way in real life, he'd be kicked off the force. Handwaved by Mosely taking the case to the Feds who did not care about such details.
Especially if police knew Gabriel was doing research for his books, given that some were in league with the Voodoo cabal and were trying to keep the details of the murders a secret.
And the level of influence of said cabal would also count as an acceptable break from reality.
The presence of a ribcage is supposed to prevent one from tearing out one's own heart. Since the person in question was a Schattenjaeger, perhaps A Wizard Did It.
Affably Evil: Dr. John in the first game and Von Glower in the second.
Alignment-Based Endings: In Sins of the Fathers, Gabriel can choose at the end whether to try to save the possessed Malia from the pit she's dangling over, simply let her fall to let Tetelo die, or try to actively kill her to achieve the same.
As You Know: Some of the dialogue trees in the first game run into this.
Apocalyptic Log: Acoording to a newspaper clipping from the year 1810, in Charleston SC, The Voodoo Murders have been happening ever since the early 19th Century. Also according to Gunters Journal, Gabriel discovers that this whole evil started as far back as the the 17th century.
Big Bad: Malia Gedde, In Gabriel Knight: Sins of the Fathers.
Big "NO!": In the first game, when Gabriel first sees Tetelo possess Malia, after Wolfgang tears his own heart out so Gabriel can get the Schattenjäger amulet, and when Malia willingly falls to her death.
There's also one in the second game, when it dawns on Gabriel that he killed the wrong werewolf, and is now cursed to become one.
Bilingual Bonus: In the Beast Within most articles, notes and conversations written or spoken in German are never translated, partially to emphasize Gabriel's inability to communicate in this language.
Likewise with the "Drei Drachen" poem in Sins of the Fathers. It's even creepier if you know German.
And of course, 'Ritter' is German for Knight.
Sins of the Fathers has some Creole French. You may even figure that "cabrit sans cor" means a human sacrifice.
Bittersweet Ending: GK3 ends on a heartbreaking downer. Even though Gabriel prevents the Night Visitors from acquiring the blood of Christ, he returns to the hotel to find that Grace has left him and written him a note. It's implied that it says she left because she is uncertain of her relationship with Gabriel and has left in order to think about it. Even though he's saved the world, Gabriel is not able to get Grace. Doesn't help matters either that just moments before finally decided that he was in love with her.
But Not Too Black: Malia Gedde has a bronze skin color, especially compared to Dr. John. This is Justified however as Tetelo is "black-black" and Malia is implied to be the descendant of her and the German Gunter.
Butt Monkey: Mosely, very much so. The guy has pretty rotten luck in general and Gabriel also tends to take frequent advantage of him.
Cat Fight: In The Beast Within, Grace and Gerde, albeit verbally and nearly one-sided from Grace. In GK3, Grace and Madeline.
Characterization Marches On: In Sins of the Father, Gerde was little more than a slightly helpful maid in Yodel Land costume (although what she says [or doesn't say] about Wolfgang at least implies what is later stated explicitly). In Beast Within, where Grace has far more interaction with her, not only is she dressed more modernly, but she also comes into her own as a character, especially given the knowledge that she was in love with Wolfgang.
Chekhov's Skill: If you ask Mosely the right questions near the beginning of the game, you learn that he and Gabriel used to play Monkey in the Middle when they were kids. When they fight Tetelo, this hobby comes in very handy...
Chess Motif: Near the end of GK3, there's a puzzle involving a chessboard. In order to solve it, Gabriel must move in the style of the Knight piece.
Church Militant: Schattenjägers (in English, it means "Shadow Hunters"), a sort of a German Inquisiton.
Gabriel Knight's family does comes from a long line of Shadow Hunters.
Continuity Nod: In Sins of the Father, when trying a certain action on Grace, Gabriel's fourth-wall comment is 'Don't mind if I do!'. Doing the same with the French tour guide in the third game results in 'Mind if I do!'.
You can see the scars on Gabriel's arms that he sustained in Sins of the Fathers in the opening sequence of The Beast Within. On the other hand, while there are clearly scars on Gabriel's right arm, Malia wasn't in any position to cut anything other than his left arm.
Corrupt Church: In Sins of the Father, the St. Louis Cathedral is a front for the Voodoo cabal.
Cowboy Cop: Arguably Mosely, who does things for Gabriel he probably shouldn't.
Crouching Moron, Hidden Badass: While Mosely's not exactly a moron and is a competent enough cop, he's still enough of a dorky Butt Monkey that finding out he's working for the CIA in GK3 is quite a level of implied badass.
Through much of SOTF he looks little more than a piece of fat sitting in his office and allowing Gabriel to take advantage of him. The ability to think and act quickly he demonstrates in the crypt, where Gabriel mistakes him for dead, and which is revealed only in the last day, comes as a shock. And dispatching the fearsome Dr. John with a single shot may count as his moment of awesome. And then he catches a solid gold (read: incredibly heavy) medallion with one (injured) hand.
Curse Escape Clause: Killing the very source of a werewolf's infection will end his curse. This becomes very important after Gabriel is infected and he must find and kill the head of the Bavarian werewolves to become human again.
Darker and Edgier: Part of the reason these games stood out? They were Sierra entertainment games that not only had a serious plot, but complemented it with a Darker and Edgier setting to fit. Not to mention, they were for older players, but weren't enforcing strict adherence to code like Police Quest or adult like Leisure Suit Larry.
Dating Catwoman: Gabriel's relationship with Malia in the first game and arguably Von Glower in the second.
Dragon-in-Chief: He's much taller, stronger, and more malicious than Malia, and he has no qualms about killing Gabriel Knight even when Malia specifically ordered him not to: "DJ, keep eyes on GK but do not harm." At least he doesn't attack until Gabriel goes where he shouldn't.
Dream Sequence: Gabriel experiences a dream during his first visit to Schloß Ritter, which proves to be a metaphysical means for him to take up the title of Schattenjäger.
There's another in The Beast Within in which Ludwig shows Gabriel the last actions of his life, which helps Gabriel solve the case, and free himself from the werewolf curse.
Grace also has a dream sequence early on in The Beast Within, in which she's fleeing from a pack of wolves and gets rescued by Ludwig, only for him to turn into a wolf as well. It turns out to be significant foreshadowing of the plotline.
Early-Bird Cameo: If the player has Gabriel investigate the Schattenjäger library in SOTF, he comes upon books relating to werewolves and vampires, the antagonists in the next two games.
Heck, to compensate for the fact that you can't die during the first 90% of each of the games (which is kinda unique in Sierra games), most of the deaths that do occur in the last sequences are in fact usually pretty gruesome. Getting your heart ripped out or your jugular slashed or strangled by a snake, getting your throat ripped open by a werewolf, getting sliced in half or your spine broken by being "folded the wrong way" are all part and parcel of the uglier side of the Schattenjäger business.
Gratuitous German: But then, who really wants to ditch the word Schattenjäger in exchange for its boring translation, "shadow hunter"?
Hesitation Equals Dishonesty: Every single one of your suspects in installment three will hesitate before claiming they are merely... taking a morning stroll... when you encounter them under suspicious circumstances, and their binoculars are just for... birdwatching, yeah. Mosley in particular spends half his early game dialogue dot dot dotting away at you.
Hell, just check out the imdb page, and prepare to have your mind blown.
Human Sacrifice: Features heavily in Sins of The Father. "Cabrit sans cor."
Hoist by His Own Petard: The villain of the third game summons a demon to kill Gabriel. Gabriel killing the demon kills the villain.
Hollywood Voodoo: Zig-zagged - the first game actually contains a pretty detailed history of Voodoo, also mentioning Vodoun, Loa, Hoodoo, Gris-Gris, importance of certain holidays in Vodoun, etc. Justified in that most of the places you learn this from are in fact, a museum dedicated to Vodoun - they've Shown Their Work there. In fact, the media dubs the murders done in a ritualistic fashion the "Voodoo murders" because, well, they're more famliar with Hollywood Voodoo themselves!
The aversion comes from the fact that the Big Bad is controlled by a former slave and voodoo priestess named Tetelo.
Hyperspace Arsenal: Lampshaded at one point in Beast Within, when Grace comes upon a quite large "PRIVAT" sign, about as long as someone's torso. To show that she's taking it with her, the actress — the camera's POV being from the neckline up — holds it upright and slides it down... somewhere... and then turns back around and walks back towards the camera. There's no noticeable bulge in her clothing, and she's not wearing her large coat at the time. It's actually rather amusing.
Hell, at one point she has a pigeon wrapped in a pillowcase stuffed into her coat, which she then smuggles past a bunch of guards at a major tourist attraction.
Inverted once with Gabriel in the first game. If you take money from the hounfor storeroom several times, Gabriel will start saying that he can't take any more.
In Medias Res: 3 starts with an abstract at best opening video, after which Gabriel spawns in his hotel room without a single line of exposition. The player has to piece together what he's doing in Rennes-Le-Chateau through NPC conversations.
All There in the Manual: The immediate leadup is instead detailed in a short comic that came with the original releases of the game.
It Gets Easier: Or so Grace tries to convince Gabriel, at the end of The Beast Within, when he's quite despondent and feeling guilty about the events of the game and his reponsibilities as a Schattenjager. His expression shows rather clearly that he doesn't believe it.
Gabriel, Mosely, and Grace form a sort of dysfunctional one in all three games, though poor Mosely doesn't really stand a chance with Grace.
Possibly Gabriel, Malia, and Grace in the first game as well, depending on whether Grace was jealous of Malia (as Gabriel claims) or merely suspected that she was dangerous (as Grace herself claims).
Grace thinks there's one between her and Gerde in GK2 (causing a one-sided Cat Fight), until she finds out Gerde actually loved a different Schattenjäger.
A more straightforward example between Gabriel, Grace and Madeline in GK3.
Magical Database: In GK3 Grace creates SIDNEY (Schattenjäger Information Database), a computer database of information relevant to Gabriel's cases. It in turn is based on the library of actual books that the Schattenjägers maintained in Castle Ritter for the same purpose.
The Maze: Bayou St. John in the first game. You can't navigate without a tracking device.
Made of Iron: Dr John is every bit as resilient as he is big. In certain death scenes he takes a roundhouse kick to the face or several right hooks to the jaw followed by several blows to the stomach. None of them even make him flinch.
Meaningful Name: Gabriel Knight, hearkening to the angel and the job, of course; furthermore, the name "Ritter" is a German title meaning roughly "knight" and translates literally into "(a male) knight."
Messy Hair: Gabriel's hair perpetually looks like he just woke up. Actually is a plot point when in GK1 he has to flatten and smooth it down with hair gel to pass as "Father MacLaughlin".
Moon Logic Puzzle: GK3's infamous "cat hair mustache" puzzle, which Old Man Murray used as an example of how adventure gaming killed itself and which is the inspiration for the current trope image. You must make a fake mustache to disguise yourself as a man who doesn't have a mustache (after drawing one on his ID) by scaring a cat through a hole you've rigged with tape and then affixing the stolen cat hair to your lip with maple syrup. 'Cause that's what makes the disguise pop.
Actually, the "get a fake mustache to disguise yourself as a man without a mustache" thing makes sense in a way, since Gabriel and Mosely look nothing alike, but having a big moustache on both the man and the photo can well cause a casual observer to think "yep, same guy". As to how you get it and how you attach it to your lip... no excuse.
Multiple Endings: The first game has two possible endings depending on whether you try to pull Malia out of the chasm, try to push her, or do nothing during the finale. Since there were sequels, only one of them is canonical, as Malia kills Gabriel if he doesn't try to save her, or kills herself if he does.
No Canon for the Wicked: The "neutral" and "evil" choices for the ending of GK1 result in Gabriel's death, which obviously isn't canon.
Non-Standard Game Over: In The Beast Within, if you mess up at the point where Gabriel is in the dressing room in the theater you get an ending of sorts where you see a newspaper article stating that Gabriel has disappeared, presumably either killed in wolf form or taken away by Van Glower, and, even worse, Grace is the prime suspect in his murder because of all the strange things she was doing to actually help him.
Novelization: The first two games were adapted into books by Jane Jensen.
The Obi-Wan: The aging uncle, Wolfgang Ritter, serves as this to Gabriel.
The Other Darrin: Dean Erickson replaces Tim Curry as Gabriel in The Beast Within. Curry returned for the 3rd game.
This depiction is, however, way more consistent with European folklore than most portrayals of werewolves in fiction.
Pay Evil unto Evil: Tetelo's victims in the backstory of the first game, and Malia's victims in the game itself, were mostly criminals and ne'er-do-wells.
People's Republic of Tyranny: Implied in Sins of the Fathers. While we don't see very much corruption in the People's Republic of Benin, nobody seemed to give Gabriel too much trouble over transporting a dead body (with its heart cut out) from Benin to Germany.
Recurring Riff: "When the Saints Go Marching In" appears in all three games.
Red Herring: In the first two games, you find something that is highly unusual in point-and-click adventure games: an inventory item that has no use whatsoever, not even to kill you. The photo of young Mosely in the first game, and the rough draft of Gabriel's manuscript in the second.
Religion of Evil: One of the driving questions of the first half of the game is determining whether the "Voodoo Murders" are being committed by a twisted Voodoo cult or whether it's just a smokescreen. The true culprits are an insane cult of Voudoun practitioners, a religion practised in certain countries in west Africa from which the various versions of Voodoo is derived, who claim themselves to be descendants of the Gedde Tribe. They worship Ougun Badagris, the Lord of Destruction, and their leader is possessed by the Loa (ancestral spirit) of Tetelo, an African slave and Voodoo priestess who died hundreds of years earlier.
Romantic False Lead: One in every game for Gabriel. Malia in Sins of the Fathers and Madeline in Blood of the Sacred, Blood of the Damned are classic examples. The Beast Within has a more convoluted example: Grace believes that Gerde and Gabriel are somehow involved, but in fact Gerde was Wolfgang's lover, while the nominally heterosexual Gabriel is in fact engaging in some very deliberate Foe Yay with Von Glower.
Scary Black Man: Dr. John from Sins of the Fathers has a calm, learned demeanour, but he towers over everyone else and is heavily muscled, making him an intimidating person to be around. Late in the game, he is revealed to be the right-hand man of the Voudoun cult, and is responsible for almost all possible deaths after he is revealed to be such, typically killing Gabriel with his bare fists.
Scenery Porn: You, as Grace, get to visit Ludwig's castles Neuschwanstein and Herrenchiemsee in Beast Within. And because you're looking at photographs of the real things as your backdrops, they. Are. Gorgeous.
Concept art for the 20th Anniversary remake of Sins of the Fathers looks to be this way.
Screw the Rules, I'm Doing What's Right: Gabriel takes Mosely's credit card and charges a trip to Germany, a trip to Africa, and back to the united states on it. Suffice to say...even in the time frame the games are set in, Gabriel should be in legal trouble. And that's saying nothing of copying police files that he was specifically told not to copy, stealing Mosely's badge, and having a dead body transported from Benin to Germany.
Shout-Out: One of the messages on the bulletin board at Tulane University in Sins of the Fathers is about a lecture on investigative journalism by an elderly Laura Bow Dorian. Laura Bow was a student at Tulane in the '20s, and Sins of the Fathers takes place in the '90s.
In GK3, there's one to Dune when Gabriel asks Wilkes whether he's trying to call a Sand Worm with a thumping device.
Shown Their Work: Say what you will about the writing. The plots and settings interweave various truths and mythologies extremely well.
Not to mention the detail of many locales in New Orleans in the first game. (someone went as far as taking photographs for comparison purposes).
The first game, Sins of the Fathers, uses the past misdeeds of ancestors haunting their descendants as the primary motivation for the story, as well as a constant theme. Gabriel's family is seemingly cursed to have the father of each generation die when the child reaches eight years of age, and a mistake by one of Gabriel's ancestors is directly responsible for the story. When Gabriel's ancestor found out that the woman he was romancing happened to be a member of a dangerous cult, he condemned and betrayed her rather than giving her a chance to repent that she might have taken, causing her to steal the powerful Ritter artifact that allowed her cult to flourish into the twentieth century.
The theme of ancestors having committed crimes that their descendants must answer for pervades The Beast Within; Von Glower inherited the werewolf curse from his father (who gained it through a Gypsy Curse after raping a young girl).
Taking You with Me: If you choose not to attempt to rescue Malia at the end of Sins Of The Fathers, she will drag Gabriel down the fiery abyss with her.
Tarot Troubles: Mrs. Smith can be prompted to do tarot readings for Grace and an absentee Gabriel. Similar to Phantasmagoria, the cards' meanings are incorrect, but it at least tried to break the tendency towards major arcana cards by including a Two of Wands in Gabriel's reading.
Thanatos Gambit: King Ludwig comes up with a truly spectacular one, involving Wagner's lost opera, crystal chandeliers, and acoustics at a famous theatre. When he is unable to put it into effect himself, he hides the opera throughout his castle, entrusts a diagram to a village woman, and writes a letter to his cousin Empress Elizabeth, hoping that she will do it in his stead (the novelization reveals that a spiteful servant burnt the letter). Over a hundred years later, Gabriel and Grace finally put his plan into action, successfully freeing both Gabriel and Ludwig from the werewolf curse.
That Was the Last Entry: Gunter's journal. It's pretty obvious he committed suicide when he writes stuff like "These final words" and "I pray [...] that my punishment in Hell will be long and bitter."
Unwinnable by Mistake: in Sins of the Fathers, if you don't pick up masks and cloaks for yourself and Mosely before reviving Grace, tough luck. Dr. John comes into the room and promptly kills you both.
In the first day of GK3, if you go straight to the church after the second part begins and speak with people there, the scene with certain guest exchanging rooms doesn't happen, and after speaking to Mosely, you can't progress further. Doubles as a Game-Breaking Bug.
Voodoo Doll: There is one Displayed in The Historical Voodoo Museum.
It reminds Gabriel of Grace, apparently because it's so spiky.
What the Hell, Hero?: Mosely in particular lives to Lampshade this trope. Most obvious in GK3, when he calls Gabriel out for his treatment of Grace.
What the Hell, Player?: In Sins of the Fathers you can try out the various non-speaking icons on Grace. If you click "look," "take," "move," etc., Gabriel will indulge in a little fourth-wall commentary about his attraction to her. If you try to "open" Grace, however, Gabriel says, "I don't even want to think about what you mean."
Will They or Won't They?: It's obvious from the start that Gabriel and Grace care for each other, but they don't start to show this until towards the end of Beast Within. Their first actual consummation in Gabriel Knight 3 is followed by very awkward periods between the two, as well as with those around them.
Yodel Land: Gerde's outfit in Sins of the Father shows signs of this. In Beast Within, her actress wears much more sensible and modern clothing.