Treacherous Advisor

Also called a Mentor Mole, a Treacherous Advisor character is the type the Heroes consult when they're digging up an Ancient Conspiracy, or something of the sort, and have hit a dead end. Surely he's in a position to be helpful? After all, he's the scholar/politician/military man/whatever, and just likely to have the information they need. Not to mention he can keep a secret.

Unfortunately, this trusted expert is secretly one of the bad guys. Sometimes he may actually be the Big Bad. What makes him different from your average Mole is the degree to which the heroes require his assistance -- he's not a regular part of their team, but he's the only person who can give exactly the help needed.

The dead giveaway for this character type is accepting the heroes theories with a complete lack of skepticism. If it were anyone else, the first thing out of their mouth would be, "Why should I believe you?" If the character says "Have you told anyone else?" or "It's a good thing you came to me." be warned: they're either about to give The Reveal or planning on making some calls and starting a massive cover-up as soon as the hero leaves the room.

Another common trait of Treacherous Advisors is storing the Plot Coupons the heroes are fetching, revealing themselves once they have the last one. In these cases, a common giveaway is their seeming a little too interested in the Plot Coupons, more specifically in the act of actually taking them. A dead giveaway is if he doesn't let the hero look at the ones he's already collected. The hero will sometimes catch on as he's returning the last one, but never before then.

In a Tournament Arc, the Treacherous Advisor may be the one who helps the hero reach the finals because he (or his Big Bad boss) has a trap waiting in the final round.

This is generally a subversion of the more typical Mentors or Reasonable Authority Figure, whom the character seems to be until The Reveal.

On rare occasions, everyone of importance whose help the hero seeks is a mole; the hero's only real allies are the ones with no power or influence.

Not to be confused with the Evil Chancellor. Contrast Sarcastic Devotee. Despite its name, the Evil Mentor and this trope rarely overlap as the Evil Mentor will not try to hide its true nature.

WARNING: Examples can be major spoilers for a climactic reveal. Read ahead at your own risk.

Anime and Manga

 * Gil Graham in Magical Girl Lyrical Nanoha A's.
 * Subverted in Yu-Gi-Oh GX: Daitokouji-sensei, Judai's teacher and ally, was revealed to be The Mole, and then later The Mole for the good guys.
 * in Naruto's Chuunin Exam Tournament Arc.
 * in G Gundam.
 * in Fate/Stay Night.
 * Words Worth: Both Tessio of the Shadow Tribe and Menza of the Light tribe, who are later revealed to be
 * Big Bad  from Tiger and Bunny is this to

Comic Books

 * in Knights of the Old Republic. He manipulates Lucien Draay into doing some truly nasty things- including ordering the deaths of several of his colleagues apprentices and trying to kill his own- because that was supposed to prevent the return of the Sith..
 * In Bookhunter, after the Library Police finally retrieve the stolen book, Agent Bay realizes that the stolen copy was actually another forgery--because the original book had already been stolen by the Chief of Library Security.
 * In Spider Man, when NYPD criminologist Carlie Cooper discovers Officer Vin Gonzales is part of a conspiracy to frame Spidey, she goes straight to the precinct sergeant. He turns out to be deeper in it than Vin, and quite prepared to pin the whole thing on Vin and Carlie.
 * In All Fall Down, is this to Siphon and the Pantheon. Mildly subverted in that he is legitimately looking out for IQ Squared's best interests.

Film

 * The main antagonist in Prince of Persia the Sands of Time.
 * In Another 48 Hours, a Retcon makes Jack Cate's fellow officer and longtime friend Ben the Big Bad whom Reggie Hammond had robbed in the Backstory to the first film, and the one who has been feeding Jack misinformation all along.
 * Indiana Jones and The Last Crusade. Both  would qualify.
 * from the Iron Man movie. Not a big secret to those who know his history from the comics, but in the film,
 * in Magnum Force
 * Captain Corso in Titan AE.
 * A rare example who goes to the trouble of searching out the not-yet-hero, convincing him to join their quest if only for a nicer place to live, inspiring him to believe in a cause other than his own self-interest or personal profit... and then revealing himself to have been working for the bad guys all along just for a big check? Why bother turning the cynical youth into a heroic idealist just to get him to lead you to what you want? Just offer the cynical youth a cut of the cash (and THEN betray him anyway if you don't feel like sharing).
 * Because he figured, possibly incorrectly, that Cale was an idealist who couldn't be bribed. And if he offered him money, Cale would start to be suspicious of his motivations. If he offered him money from the alien species that destroyed Earth Cale would likely try to kill him. If that failed, he'd knew off his own hands with horseradish to screw over the Drej.
 * in Unbreakable.
 * in Heavy Metal 2000.
 * The B-movies Full Contact (1992), Dragon Fire (1993) and Bloodfist 2050 (2005) all use exactly the same plot: a kickboxer who participates in the underground pit-fighting circuit in order to find the guy who has killed his brother. In each one, it turns out that the killer is the mentor who trained him.
 * The film version of Watchmen adds shades of this to the relationship between.
 * in "Memento".

Literature

 * , the central villain (out of many candidates) in The Da Vinci Code.
 * Saruman in the The Lord of the Rings books (and especially in the movies). Grima Wormtongue also qualifies.
 * Captain Dudley Smith in L.A. Confidential.
 * Chauncy in The Dresden Files.
 * This is also a big part of how the Fallen operate: If you pick up one of the Blackened Denarii you get an ancient, superintelligent and ridiculously powerful Spirit Advisor who'd be happy to show you how to solve any problem you run into -- until you're so dependent on its help that it can control you completely.
 * J.K. Rowling really likes this trope.
 * in Harry Potter and the Philosopher's Stone.
 * in Harry Potter and the Chamber of Secrets.
 * Subverted in Harry Potter and the Prisoner of Azkaban when.
 * Although not canon, many fanfiction writers speculate that
 * in Harry Potter and the Goblet of Fire, whom Harry and co. frequently consult for help solving the mysteries.
 * Harry Potter and the Half-Blood Prince
 * In Boris Akunin's Fiction, we have Ivan Panteleevich, leader of an elite Soviet sports club. Sergei Dronov, one of the superpowered protagonists, was discovered and saved by him early in the book, and has followed "the Sensei"'s advice ever since, leaving the life of crime and becoming a sports celebrity and a powerful businessman during the Perestroika. In the end, it turns out that the Sensei was Mind you, he's not necessarily evil, inasmuch as he seems to genuinely want to help Dronov and is mostly concerned with
 * In Winter Queen (an earlier Boris Akunin novel), there is.
 * Romance of the Three Kingdoms has several, including one who served Liu Bei but was tricked into serving Cao Cao; he refused to give meaningful advice from then on and kept his mouth shut when he saw through the ruse at Chi Bi. More importantly,.
 * In The Kingdoms of Evil: De Macabre for certain, and possibly everyone else in Skrea.

Live Action TV

 * In the Doctor Who episode "Invasion of the Dinosaurs", Sarah Jane Smith falls victim to this trope twice. First, the man she sees for help finding the villains' base turns out to be the one who helped them set it up. Then, after she escapes from him, she takes what she knows to the general who is coordinating the state of emergency, not knowing that, while she was away, he had also been revealed as a member of the conspiracy.
 * From Heroes: Claire has been hiding from her father the fact that she heals incredibly fast. She finally can't take the pressure anymore and decides to tell him... and he tells her he already knows, and asks her whom else she's told. Subsequently, every person she mentions has their memories of it wiped, and Claire herself is targeted for a wipe.
 * In somewhat ironic fairness, though, HRG was trying to protect Claire [and the others] by doing this.
 * From Buffy the Vampire Slayer: Gwendolyn Post (played by Serena Scott Thomas), the dark magician who poses as Faith's new Watcher, and "Doc" (played by Joel Grey), the strange old man/demon who helps out Dawn but is also working for the enemy.
 * in John Doe
 * in Season 2, ep. 2 of Life On Mars.
 * Subverted in one episode of Stargate Atlantis: When visiting the ruins of a ship that had the crew both in stasis and believing that they were still flying the vessel in a virtual reality setting, the second in command apparently was planning to do something against her boss. However, its later revealed that the actual second in command was killed long before the events of the episode by a Wraith, and a Wraith (presumably the same one that killed her) was impersonating as her.
 * Merlin has Agravaine as a good example of this. Arthur's uncle and advisor, as well as The Mole. Merlin and the rest eventually figure him out, but Arthur takes the longest to quit trusting him.

Video Games

 * in Terranigma. Also
 * From Assassin's Creed
 * GLaDOS from Portal. "The Enrichment Center is required to remind you that you will be baked and then there will be cake."
 * In both Metal Gear and Metal Gear Solid, the player-hero receives advice via radio
 * In a variation, in all three Metal Gear Solid games,, is advising and betraying the game's Big Bad on behalf of a singular third party. How does he keep getting away with this? Impressively.
 * Subverted in Metal Gear Solid 4. Drebin . He also makes it clear from the beginning that he works for everyone who can pay him, and is telling the truth when he says he won't betray his customers, Snake included. He even saves the man's life on occasion.
 * Final Fantasy X can be considered the apotheosis of the concept. The party's initial quest is a voyage to seek aid in destroying the monster Sin;
 * In the first Ratchet & Clank game, our heroes initially try to alert local superhero Captain Qwark to the Blargg threat, but discover that he's actually working with Chairman Drekk, who's offering him a substantial amount of money and fame for sponsoring their new homeworld.
 * in Jade Empire
 * He's particularly insidious because.
 * Oh, man...He was running one hell of a Xanatos Gambit the entire time, with as the Unwitting Pawn.  Magnificent Bastard in every way.
 * In the old C64 game Bard's Tale 2, the goal was to find the pieces of the Destiny Wand in order to defeat the big bad Lagoth Zanta. Every time you found a piece, you needed to get hints to the location of the next one by paying a character known as the sage.
 * Persona 2 features a variation; in both games, the Time Count provides useful services -- ones that can't be gotten anywhere else in Eternal Punishment. He turns out to actually be an avatar of Nyarlathotep, the Big Bad. Unlike most examples, it's not part of some overarching scheme -- being a trickster and manipulator, he decided it'd be more fun this way, and arrogantly believed that even if he helped them, the heroes couldn't possibly defeat him.
 * In Persona3,
 * In Bio Shock,
 * In Vexx,
 * Ultima VII plays with this a bit by linking it to a Chain of Deals. In order to contact the Time Lord, whose help is necessary to stop the Guardian from dominating Britannia, you need to get help from the Wisps - interdimensional information-brokers who, in exchange for the help, want you to acquire information for another client of theirs. The information in question is a notebook on the Guardian and his puppet church, the Fellowship, composed by one of the few Britannian scholars aware of the Guardian's existence. Turns out, their client is the Guardian, who, having found out what his opposition knows about him, then has him murdered.
 * In Fire Emblem: The Sacred Stones, the high-ranked Paladin Orson leads Prince Ephraim and his group into a direct trap, having betrayed his country since the enemy promised to revive his deceased wife.
 * In Radiant Dawn,.
 * In Tales of the Abyss,
 * Subversion in Super Robot Wars, especially on Mizal Touval, the Shura Advisor (because, he is not on the player's side all the time). He actually had plans on his own, that is to overthrow the Big Bad and usurp his power on his own. But he never got lucky in his endeavor, because:
 * In Unreal 2: The Awakening, the main character's rather paternal commanding officer sends him on a Fetch Quest to assemble Plot Coupons, ostensibly under orders from The Federation to keep it out of the hands of the Always Chaotic Evil Skaarj..
 * In Apollo Justice: Ace Attorney, in the first case,
 * Castlevania: Order of Ecclesia has


 * In System Shock 2,
 * Princess Waltz features a really disturbing one,
 * Or.
 * in Code Name: Viper is actually the guy behind the South American drug ring you've been commissioned to stop.
 * In Mantra, the plot of the game is that Saric (the player character) is supposed to retrieve the Mantras of fire, earth, water, air, and force to help out his master, the Ambassador, in his negotiations with the evil magician Balther. Late in the game, however, you find out that.
 * Subverted by  in Rockman.EXE 6, as he is not truly treacherous.   He then arranges a meeting with Netto to explain
 * The original Mercenaries has Josef oust Sergei as leader of the Mafia near the end of the game; probably not all that surprising, since 1) this is The Mafiya we're talking about, 2) Sergei is an airheaded Ted Baxter, 3) Josef is ex-KGB, and 4) they foreshadow the hell out it by showing Josef having practically undisguised contempt for Sergei's bumbling and snotty attitude.
 * To be fair, Sergei tried to have the player character and Josef taken out by the North Koreans first, then Josef launched his coup (though given Josef's demmeanor, Sergei was living on borrowed time anyway).
 * In Bunny Must Die, Bunny, upon receiving her curse, meets up with a fat messenger of God who offers to lead her to the Cave of the Seven Devils to remove said curse -- and gets gored by a stag shortly upon their arrival. By the time she's slagged all the other devils and beaten Chelsea to a pulp, she finds him, fresh as a daisy, and he tells her that he set the plant to blow once she was near it. All of this just to give her a reason to get him all his power back.
 * King Lemele in The 7th Saga.
 * in Anachronox.
 * in Star Wars: The Force Unleashed.
 * in Cocoron.
 * In Call of Duty: Modern Warfare 2,.
 * in Jak II is the Metal Head Leader.
 * Sindri Myr to Chaos Lord Bale in Dawn of War, leading to one of the most Narm-filled moments outside of the Soulstorm expansion.
 * In Okami, you wind up consulting High Priestess Rao for help fixing the cursed mess that is Sei-an City and the Ryoshima Coast. Too bad she'd been killed months earlier, and you turn out to have been dealing with Demon Lord Ninetails, who was responsible for a lot of it and had been trying to use you as a MacGuffin Delivery Service for the Fox Rods or, failing that, get you killed. It works pretty dang well, too, and only some very quick thinking and a Heroic Sacrifice on Queen Himiko's part allow Ammy to stop Ninetails.
 * In Psychonauts,  is the real Big Bad behind Doctor Loboto.
 * In Wario Land 3, Wario gets advice from a sealed away mysterious figure, who will apparently give him riches and power if released. But sadly for him, it turns out this figure is actually Rudy the Clown, an Evil Clown who conquered said pocket universe the game is set in, and transformed all the people into monsters.
 * In Sacrifice,
 * In The Settlers 7 campaign, Princess Zoe is sent by her father to save the kingdom of Tandria from the evil Lord Wolverine who usurped the good King Balderus. She is assisted by a kind old barkeep who
 * Many of these in Alpha Protocol, but the gold medal goes to
 * Well, actually,
 * In Dark Star One, give Kayron his father's eponymous ship and sends him on his quest. In the end, he turns out to be Kayron's father's killer.
 * In Asuras Wrath, offers Asura cryptic advice several times in the game  to aid him in his battle against the Deities.
 * Luigi has an offscreen adventure in Paper Mario the Thousand Year Door where he collects the pieces of The Marvelous Compass to rescue Princess Eclair under Minister Crêpe's guidence.
 * In Asuras Wrath, offers Asura cryptic advice several times in the game  to aid him in his battle against the Deities.
 * Luigi has an offscreen adventure in Paper Mario the Thousand Year Door where he collects the pieces of The Marvelous Compass to rescue Princess Eclair under Minister Crêpe's guidence.

Webcomics

 * Miranda West in The Wotch may qualify for this, given that she's keeping some very big secret from protagonist Anne and that she's willing to totally destroy the lives of a few people in order to make sure nobody interferes.
 * (Not gonna bother using spoiler tags since there's only one advisor-type character in the comic, but) Panthera has Reynder/Ari, who turns out to be Oosterhuis.
 * In Pibgorn, a succubus can see that our heroes still find him useful.
 * Nicodemus, the Big Bad of The Dreamland Chronicles got his start as one of these. Notably, he actually told his liege in advance that he would betray him, though he made it clear that he would only do so if his liege continued what Nicodemus considered to be a self-destructive policy. His liege didn't stop. Nicodemus was true to his word.

Western Animation

 * in Transformers Animated.
 * In Exo Squad, Barca plays this role in his attempts to get Halis to assassinate Simbacca.
 * In the Men in Black Animated Adaptation, Kay's first partner and mentor Alpha turned out to be a scheming bastard. When Kay refused to join him, Alpha shot him and left him for dead. It's no wonder Kay became an emotionless robot after that.