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Fanfic / The Citadel of Truth

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The Citadel of Truth is an Adventure Time fan fiction created by Ooobserver that centers around the pairing between Finn and Flame Princess.

Having lingering feelings for the queen, Finn unsuccessfully tries to enter the Citadel and disperse the barrier between him and the Flame Princess. However, with support from his girl and his personal blacksmith Ferrum, Finn tries once more to conquer the trials of the Citadel, only for him to discover a whole new world filled with people that he never knew before, including an ancient evil set out to conquer the universe...


The Citadel of Truth provides examples of:

  • Action Girl: Without the efforts of Flame Princess, Finn would have not managed to continue on with his journey across the multiverse.
  • An Arm and a Leg: Finn lose his right arm as a result of the Lich's attempt of Taking You with Me.
  • Arc Words: "Mistakes aren't supposed to burden you; they're supposed to shape you".
  • Armor-Piercing Slap: Flame Princess slaps Finn a lot, whether she demands to know what Finn is hiding from her or trying to get his attention.
  • Artifact of Doom: The Shards of Evil that is claimed by Astrum, are used to corrupt and empower the deities with dark powers.
  • The Assimilator: This is Astrum's special power; he gains the appearance and power of the person that he recently killed.
  • Battle Couple: Finn and Flame Princess fight Astrum's oppositions together and they are consistently good at that.
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  • Benevolent Genie: The orb of Citadel can read into a person's mind and grants the wish that the person exactly desires no matter how vague the wish is.
  • Beta Couple: Ferrum and Flara as the beta to Finn and Flame Princess.
  • Big Bad: Astrum the siphoner. However, he is not the Final Boss, that title goes to The Lich.
  • Blatant Lies: When Jake asks why Finn's lips are burnt due to kissing Flame Princess earlier without the Flame Shield, he makes up a lie about how he fell down into the floor of the Fire Kingdom. Nobody is convinced of his lie.
  • Brought Down to Normal: Using a magical lantern, Ash absorbs the powers of the entire gang (Sans Flambo) to the point that they rely on Finn to guide them.
  • Conservation of Ninjutsu: While multiple evil Finns that invade the Nightosphere are a big trouble for the heroes, the sole survivor of the invasion is much more of a threat than the other Finns put together.
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  • Continuity Nod: When Finn came in contact with the Origin, he mentions about "ruining his relationship with FP even further, let friends die, get cursed, and gets taken advantage of by a selfish father".
  • Demoted to Extra: The Lich from the series is demoted from the Knight of Cerebus Big Bad of canon Adventure Time into a material for the Shard of Evil for the present Big Bad after he is defeated by Finn and Sentin early on. Although this is later subverted as by the endgame, he immediately decides to hijack the plot and serve as the Final Boss of this fan fiction.
  • Deuteragonist: Flame Princess ended up replacing Jake in this fan fiction as the second most important character while Ferrum replaces Princess Bubblegum as the tritagonist of this fiction.
  • Disproportionate Retribution: Astrum has his own entire race killed and his planet destroyed by humans just because they fear that the Siphoners could be a threat to them. Astrum's response is to Kill 'Em All and destroy the entire universe along with it.
  • Doorstopper: Downplayed, as the fan fiction finished at 496,903 words but for Adventure Time standards, it is one of the longest fan fictions in the archive.
  • Fusion Dance: Using the power of Infinity aka Harmony's Origin allows anyone to join together in order to achieve greater power.
  • Go Mad from the Isolation: One of Finn's main test to allow access to the Citadel is to survive for centuries within a temporal space and see if he could survive with his sanity intact. His first attempt fails as he became mad at 732 years out of 800 while he succeeds in his second attempt with the help of Flame Princess despite having to stay an extra 1600 years within the dimensionnote .
  • Heel–Face Turn: After convinced by Finn to let out all of his anger, Astrum ended up realizing that what he did was wrong and in the end, decides to try and make up for all of his mistakes.
  • Heroic Sacrifice: Just as Ferrum is about to transmute his own life for Finn, Flame King offers himself to be the one sacrificed instead, stating that he would like to apologize to his wife in the afterlife.
  • Hijacked by Ganon: Just as Finn and his friends finally managed to quell Astrum's rage and convince him to make a Heel–Face Turn, The Lich suddenly decides to reappear after he is thought to have been converted into a Shard of Evil.
  • I Want My Beloved to Be Happy: In the universe where Jake and Ice King are trapped in, Princess Bubblegum is genuinely in love with Finn ( Since Marceline does not exist, at least, until Ice King wishes for her). However, when being offered a wish, Bubblegum immediately uses that wish to free Finn and his love interest Flame Princess of any boundaries separating them.
  • Kick the Son of a Bitch: Just as Astrum successfully managed to steal the Shard of Evil from Hunson, he ended up getting back stabbed by the lone evil Finn and his shard stolen. Given who Astrum is, you wouldn't really sympathize with him.
  • The Lost Lenore: Because of Ferrum's actions two years before the start of the story, he ended up scaring his lover Flara away never to be seen again. Until he ended up being taken in by his lover and reconciles their mistakes when the martians invaded.
  • The Matchmaker: Remembering how the kiss between Finn and Flame Princess in his universe managed to nearly tore the world apart, Jake decides to pair them up in an alternate universe in hopes to use its power to destroy the prism rails that made it aloft.
  • Meaningful Name:
    • Ferrum is the latin word of the element Iron, a fitting name for an alchemist like him.
    • Solara is simply the abbreviation of solar, aka sun given that she is in fact The first star and the first being to have ever existed.
  • My Greatest Failure: For Ferrum, letting his emotions out of control (and essentially break one of the most important rules of alchemy) at seeing the criminals harm his lover Flara, resulting in him destroying the Fire Kingdom dam along with a handful of fire elementals. This resulted in Ferrum scaring away Flara and put him on probation by the Fire Kingdom authorities for two years.
  • Official Couple: Finn and Flame Princess hook up quite early in the series, the focus on this fan fiction is eliminating the borders that encompasses between them.
  • Original Characters: The author introduced multitudes of OCs that appeared throughout the story starting with the alchemist Ferrum along with the Ancestral Flame. It then snowballs from here on as more and more characters are introduced.
  • Perpetual Frowner: Astrum is never directly seen smiling, unlike your typical villains. He is always seen being enraged or impatient whenever he goes towards his goals.
    • When He Smiles: However after Finn managed to quell Astrum's rage and hatred, he is seen smiling for the first time which Solara even lampshades herself.
  • The Power of Rock: Using their Harmony's Origin, Jake and Ice King uses music to directly fight Prismo and free him from the Shard's control.
  • Reality Ensues:
    • When PB tries to apologize for talking badly about the Flame King, Flame Princess reassures her that his Heroic Sacrifice does excuse his other acts such as his poor treatment of his daughter and his people but not his own wife.
    • A similar case happens in an alternate world where despite Flame Princess saving Bubblegum and Jake from their death, it still doesn't redeem the fact that FP burned Finn's right arm in her anger and responds PB to her appropriately:
    Alternate PB: This changes nothing.
    Alternate FP: It wasn't meant to.
  • Remember the New Guy?: Downplayed, as even though at the start of the story that Finn and Ferrum are close friends, we are told that they met each other at some point between the "Earth and Water" and this fan fiction.
  • Sole Survivor: Flame Princess use Finn's fear of the ocean to repel them all from the Nightosphere and ended up retreating, except for a single Finn that somehow managed to overcome his fear of the ocean and steal the shard from Astrum.
  • Superpowered Evil Side: Because Flame King has a good amount of evil energy, Finn ended up having an evil side within him as a result of Ferrum's transmutation which becomes active when either Finn battles or tries to kiss Flame Princess.
  • Taking You with Me: Just as The Lich is about to experience his final defeat, he attempts to take Finn along with him. Astrum instead takes the blow for him.
  • Turn the Other Cheek: Finn seems to forgive everyone, even the ones who dealt personal blows on him such as Cosmic Owl and Astrum himself. Of course, all those take place after he confront the issues he is currently experiencing and put them to rest (FP slapping him and help him get over the "Frost and Fire" incident started by Cosmic Owl, Finn meeting with his deceased parents whom Astrum kills and reconciles with them) so once he forgave himself, he has the capacity to forgive others for their misdoings.
  • Trapped in Another World: Due to Astrum machinations, the Adventure Time gang is separated into different universes each with a shard-equipped deity hunting them down.
    • Finn and Flame Princess are trapped in a universe where Flint becomes the main adventurer with Cosmic Owl hunting them down. However, it is later revealed that Flint is in fact, the son of Finn and Flame Princess that exists in their alternate universe.
    • Bubblegum and Marceline are trapped in a world where the mushroom bomb failed to explode and humanity is given a chance to rebuild their life. However, with Death stalking the planet, it will not be easy.
    • Jake and Ice King are trapped in a world where Marceline does not appear in this timeline ( Actually she does appear, thank to Ice King's wish), Finn and Flame Princess never met, and Bubblegum is in love with Finn himself. Unfortunately, the entire inhabitants are imprisoned under the shadows of Prismo.
  • Victor Gains Loser's Powers: Once Astrum managed to kill a person, he immediately absorbs whatever power that person possesses along with their appearance.
  • World Half Full: In the universe that Bubblegum and Marceline are trapped in, the mushroom bomb never exploded which as a result, gives humanity a second chance to rebuild their own planet.
  • Year Inside, Hour Outside: 800 years inside the Citadel's Time Room is the equivalent to 10 minutes in the outside world.

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