History VideoGame / FiendFolio

* BrownNote: Referenced with the Brown Horn, an active item that causes enemies to [[ToiletHumor fart and spawn friendly dips]]

* MasculineFeminineAndrogyneTrio: Downplayed as the only gender-related traits are in their names and [[BlueBoyPinkGirl color schemes,]] but the "basic" familiar babies become this with the addition of Sibling Syl. Sibling Syl is both in-between Brother Bobby and Sister Maggy in terms of stats and gender, confirmed to be non-binary by the developers.

** The enemies Tommy and Benny, were originally from a separate mod called ''Morbus'' and were originally called Malignant and Benign. The name change is due to an already existing enemy called Benign, which is a smaller Tumor
** One of The Sun's Minions is named Venus, after the planet. Cacophobia's avatar is also named Venus, after the roman god of beauty.

** Fiend Folio has extensive two-way compatibility with the mod ''Retribution''. However, an enemy from Retribution, a smaller I. Blob called Curdle, shares it's name with one of Fiend Folio's enemies, being a skinless Gaper variant that appears in Scarred Womb and wears a layer of flesh on its head.

** The Chest room layout "Don't make this mistake again" has two buttons and a confusing arrangement of obstacles. Pressing either boxes you in with a ton of {{Degraded Boss}}es.

!!Tropes

* DevelopersForesight: As locking characters doesn't function properly in the ''Repentance'' API, trying to play as Tainted Fiend when he hasn't been unlocked through the regular means of getting Tainted characters will send the player to an unplayable sequence where Tainted Fiend is curled up inside Home's closet, but without the original Fiend to unlock him.
** If a Slim enemy punches a solid object, it injures its hand and becomes stunned for a few seconds. This also happens if they punch a player who has transformed into stone, such as by the Gnawed Leaf or Tooth and Nail items, the Reverse Chariot tarot card... Or if they're playing as Apollyon or Golem, the two LivingStatue characters.

** Feind Folio has extensive two-way compatibility with the mod ''Retribution''. However, an enemy from Retribution, a smaller I. Blob called Curdle, shares it's name with one of Fiend Folio's enemies, being a skinless Gaper variant that appears in Scarred Womb and wears a layer of flesh on its head.

* SpoilingShoutOut: One secret room layout added by the mod features a hanging Shopkeeper. Its internal label is "[[VideoGame/DokiDokiLiteratureClub I gently open the door...]] and I find some beans" (referring to the cans of beans also in the room), which references the first major twist in ''DDLC'' caused by [[spoiler:Sayori hanging herself]].

* DamageIncreasingDebuff: Introduces the status effect "bruised", which lowers enemy defenses.

* OneSteveLimit: Thrice

Our friend Fiend, on the other hand, [[WellThisIsNotThatTrope is studying up on all those weird new monsters in the Basement, and how best to kick ass and take names]]. And it smells of fresh corn in here, all of a sudden...

* SurpriseCreepy: The nature of Fiend Folio [[BlatantLies consists solely of barrages of]] [[RapidFireComedy rapid-fire]] BlackComedy, and that's it, right? [[NightmareFuel/FiendFolio Right]]?

* AscendedGlitch: Sort of, When Clutch was added to ''Repentance'', the Clickety Clash enemies started to randomly turn rocks purple. This bug was dubbed Clutch's Curse and inspired one of the effects of the Clutch's Curse Item.

** Meltdown, a Burning Basement boss added in the remaster, loves to hit his horse as an form of attack. He'll even kill it when he gets low enough. However, since the horse was [[ItMakesAsMuchSenseInContext carrying a nuclear bomb]], it explodes and reduces Meltdown to a skeleton. [[TheDeterminator Doesn't stop him from trying to kill you, though.]]

* AscendedGlitch: Sort of, When Clutch was added to Repentance, the Clickety Clash enemies started to randomly turn rocks purple. This bug was dubbed Clutch's Curse and inspired one of the effects of the Clutch's Curse Item.

* BreakTheHaughty: The most prominent feature of Tainted Fiend is that his original LovableRogue personality is gone, replaced only with unending rage. Although, [[TrollingCreator the devs sometimes joke that Tainted Fiend is actually a separate imp named Steve]]

* DamageIncreasingDebuff: Introduces the status effect "bruised," which lowers enemy defenses.

* DontWakeTheSleeper: There's an enemy in the Depths literally called the Sleeper, appearing as a small ghost that transforms into a nightmarish figure when Isaac attempts to shoot it, or if he gets too close
* FemaleMonsterSurprise: The mod has a "Female" enemy tag that is applied to both base game and ''Fiend Folio'' enemies to be used with the Sapphic Sapphire trinket. While the mod has some enemies that are obviously female such as Ms. Dominator, there are also several enemies that are not as obviously female by first looking at them.

* LilyPadPlatform: This mod features lily pads that can be walked on but disappear for a few seconds after walking off of them.

* {{Mutants}}: Fiend is a cob of genetically-modified corn that somehow grew into a demon with human-level intelligence. China is the same, except with an apple

* ShoutOut: [[ShoutOut/FiendFolio Has its own page]]

** There's a trinket called Lost Flower Crown, which references ''VideoGame/{{Omori}}'', [[spoiler:specifically, Basil's ultimate fate near the end of the game]]. The trinket itself erases a random enemy at the start of each floor, wandering into where the chosen enemy would be will also cause [[spoiler:Something]] to appear.
* SpringsSpringsEverywhere: ''Fiend Folio'' adds rubber rocks that bounce the player, enemies and projectiles around.

** There are also two other enemies, Psychic Mr. Maw and Mobile Mushroom, appearing in one room in the Depths and Caves respectively

* BreakTheHaughty: The most prominent feature of Tainted Fiend is that what seems like his original LovableRogue personality is gone, replaced only with unending rage. [[SubvertedTrope However]], WordOfGod confirms that Tainted Fiend is actually a separate imp named Steve

* SurpriseCreepy: The nature of Fiend Folio [[BlatantLies consists solely of barrages of]] [[RapidFireComedy Rapid-fire]] BlackComedy, and that's it, right? [[NightmareFuel/FiendFolio Right]]?

* BreakTheHaughty: The most prominent feature of Tainted Fiend is that his original LovableRogue personality is gone, replaced only with unending rage.

* {{Mutants}}: Fiend is a cob of genetically-modified corn that somehow grew into a demon with human-level intelligence.

* DenserAndWackier: While it still has its share of terrifying monsters, ''Fiend Folio'' as whole leans more heavily on the "comedy" side of HorrorComedy.