Fiend

Fiend is a purple-skinned imp with horns and a devious grin, and is the titular character of the Fiend Folio MOD. He is a glass cannon character that uses his health to fight for him.

He starts the run with two Black Hearts followed by an Immoral Heart, as well as having a uniquely innate form of Pyromancy. He also holds XVII - The Stars in his pocket slot.

Abilities & Traits

Health

Fiend's Health works somewhat like ??? as he cannot have Red Heart containers, instead only being able to hold Immoral Hearts and Black Hearts.

Any effects that would give Fiend Red Heart containers will give Immoral Hearts instead.
- Items that grant Soul Hearts directly to his Health bar, however, will grant Black Hearts instead.

All Red Heart drops have a chance to become either Immoral Hearts or Black Hearts.
- This chance is affected by Fiend's Luck stat — At 13 Luck, the chance for an Immoral Heart becomes capped at about ~60%, and a Black Heart at about ~6%.
- This includes set Heart drops from items like Little C.H.A.D.
- Some special Heart types are guaranteed to be converted, with a 90% chance to convert into Immoral Hearts and a 10% chance to be converted into Black Hearts. These types are: Soul Heart, Gold Heart, and Eternal Heart.
  - Blended Hearts will instead be converted into either a Blended Immoral Heart or Blended Black Heart.
  - Bone Hearts have a fixed 1/5th of the usual chance to be replaced by full Immoral Hearts or Black Hearts.
  - Fiend can still get Eternal Hearts through other means such as items that grant Eternal Hearts directly to his Health bar, like Fate. They work as expected of normal Health ups, giving an Immoral Heart when combined or upon entering a new floor.
  - Eternal Hearts will never be converted in Angel Room-themed Super Secret Rooms.

Fiend has unique interaction with Bone Hearts. He can not add them to his Health bar like ??? but instead, they will be converted into multiple bone orbitals, like those created from Book of the Dead.

Friends

His main ability and gimmick is his Hearts turning into Minions (also known as his "friends") that attack enemies in retaliation when he takes damage.

Main article: Familiars § Minions

When Fiend takes damage while the room is uncleared, all other adjacent Hearts of the same type as the one that took damage will be removed from his Health bar and converted to Minions. For each full Heart lost, a normal Minion is spawned — with Immoral Hearts turning into Immoral Minions, and Black Hearts turning into Evil Minions — while any half Heart converted in the Health bar will turn into Hollow versions of Minions.
- When the room is cleared, every Immoral and Evil Minion will disappear and leave a Heart pickup of its original type for Fiend to retrieve. Immoral Hollow Minions spawned from Immoral Hearts will drop a Half Immoral Heart on room clear. Evil Hollow Minions spawned from Black Hearts, however, will disappear in a puff of smoke when the room is cleared, and will not transform back into a Half Black Heart.
- Fiend's Health would never convert all Hearts into Minions if it would result in his death, and will leave Fiend with at least one half of a Heart of Health remaining which will not be converted.
- Hearts of the same type that are not adjacent in the Health bar will not be converted to Minions after taking damage — for example, if Fiend's Health bar is made up of 2 () Immoral Hearts, 1 () Black Heart in the middle, and 2 () more Immoral Hearts, then only the Immoral Hearts on the right side of the Black Heart will be converted to Minions upon taking damage once, while the Black Heart and the Immoral Hearts behind it will not be converted.

Minions will follow enemies, similarly to Morsels, and deal contact damage over time to them. They deal a percentage of Fiend's Damage stat over time, and the tick rate of the damage scales with Fiend's Tear rate. Extremely rarely, a Minion can land a critical hit that deals 5× Fiend's damage, with the chance to deal a critical hit scaling with the Luck stat.
- Immoral Minions spawned from Immoral Hearts deal 20% of Fiend's Damage per tick, while Evil Minions spawned from Black Hearts deal 40% per tick, and have a higher chance to land a critical hit.
- Minions can not fly over obstacles unless Fiend himself can, in which case they will sprout wings.

If the room is already cleared when Fiend takes damage, no Minions will spawn and Fiend will keep the rest of his Health as usual.
If Fiend leaves an uncleared room through any method (including exiting the game), all Minions will transform back into their respective Heart pickups with the exception of Half Black Hearts. This is helpful if Fiend is left at half a heart after taking damage and spawning minions, as leaving and returning will let him recover his HP.

Pyromancy

With Reheated, Fiend now starts with a secondary ability — Pyromancy, in the form of launching fireballs at his foes.

Main article: Pyromancy

Fiend will generate a fireball when dealing enough accumulated damage to enemies, requiring a base total of 50 damage, and increases by 10 for every next floor. These fireballs will orbit around Fiend, and he can have a maximum of 3 at once.
Double-tapping a shoot button causes an orbiting fireball to be launched in that direction as a fast projectile with weak homing, leaving a trail of flames and exploding on contact with an enemy or obstacle.
- The fireballs themselves deals 3× Fiend's damage on a direct hit.
- Explosions can't damage the environment (rocks or doors), and do not harm Fiend.
If a fireball kills an enemy, it has a 50% chance to drop a Half Immoral Heart that flickers and disappears after 2 seconds.

Notes

Fiend's ability to generate fireballs behaves differently from the Pyromancy item, as Fiend's fireballs do not automatically generate over time, and can spawn Half Immoral Hearts from killing enemies.
- Fiend's Pyromancy is also an innate ability and not an item, and cannot be re-rolled away or removed.
Fiend has a hidden increased chance for random coin drops to become Cursed Pennies, being at 5% by default.
Fiend has a unique interaction with Fortune Worm, where he has a boosted base chance to fire fortune cookie tears than other characters.

Birthright

"Fiendish Fireballs"

Fiend's Birthright grants his fireballs a stronger homing effect, and gives them a chance to summon Hollow Friends on impact.

Unlockable Achievements

Icon	Name	Unlock Method
	Immoral Hearts	Defeat Mom as Fiend.
	Lil Fiend	Defeat Mom's Heart or It Lives on Hard Mode as Fiend.
	Imp Soda	Defeat Isaac as Fiend.
	Heart of China	Defeat ??? as Fiend.
	Fiend Mix	Defeat Satan as Fiend.
	Prank Cookie	Defeat The Lamb as Fiend.
	Pyromancy	Defeat Mega Satan as Fiend.
	GMO Corn	Defeat Boss Rush as Fiend.
	+3 Fireballs	Defeat Hush as Fiend.
	Fiend's Horn	Defeat Delirium as Fiend.
	The Devil's Harvest	Defeat Mother as Fiend.
	Fetal Fiend	Defeat The Beast as Fiend.
	Cool Sunglasses	Defeat Ultra Greed as Fiend.
	Jack Cards	Defeat Ultra Greedier as Fiend.
	The Fiend Folio	Get every Hard Mode completion mark as Fiend.
	The Bastard	Use Red Key to open the hidden closet in Home as Fiend.

Trivia

General Trivia

Fiend is a returning character from The Devil's Harvest, the predecessor of Fiend Folio of which several developers originally helped create.
Fiend himself is based off the Smiling Imp emoji — specifically, the one that Twitter and Discord uses.
Fiend shows his provocative, but very much iconic middle finger when performing his "thumbs up" animation.
If Fiend acquires the Beelzebub transformation, his appearance will change to that resembling Flysaac, another character from The Devil's Harvest.
Canonically, Fiend is genetically modified corn. This is referenced in items such as Fetal Fiend, and Fiend's Spun transformation where he is fully transformed into a corn cob.^[1]
In Fiend Folio lore, and in the lore of the imp gang designed by the developer Maria, Fiend is the boyfriend of China.
As seen in the costumes of items such as <3, Fiend's blood and internal organs are black goo. The red liquid on his face and in the costumes of some items is canonically "imp juice", a substance that fuels Fiend's pyromancy.^[2]
Fiend has unique voice lines when taking damage and dying. These were created by two Fiend Folio developers; Peas, who voiced the lines, and Happyhead, who edited them.
According to the spritesheet for Fiend's Chirumiru costume, his favorite Touhou Project character is Cirno.
When Fiend obtains Libra, half of his sprite will be orange with purple tears, bearing a resemblance to Friend, a character from Maria's iconic imp gang who acts as Fiend's rival.
In the files there are sprites for what appear to be earlier unused versions of Fiend's Minions. They appear as Immoral/Black Hearts with spider legs, with Black Hearts also having a flying version with bat wings instead.

Meta Trivia

In The Binding of Isaac: Afterbirth+ edition of Fiend Folio, Fiend was planned to have achievements and unlockables, but it was scrapped before the release. In The Reheated Update, these unlocks were re-implemented, at the player's choice.
In Afterbirth+, Fiend's fireballs were a toggle-able option in the Dead Sea Scrolls menu where they appeared and acted differently, such as being able to destroy rocks.
- Fiend's fireballs were disabled by default because the developers weren't happy with how they worked.
In Afterbirth+, Fiend had 2 different portraits depending on whether he was fighting a boss or transitioning between stages.
- Fiend's boss portrait is now scrapped due to Repentance removing the need for a second portrait (while simultaneously not allowing mods to use the two anyway).
There exists modes in the Dead Sea Scrolls menu of the MOD that can change some of Fiend's mechanics:
- With Classic Tears enabled, Fiend gains homing tears with a unique look, which were a reference to how Fiend's tears appeared in the original The Devil's Harvest MOD.
- With Imp Baby Mode enabled, all of Fiend's abilities are disabled, removing his Fireballs and having him start with 3 Red Heart Containers. Instead, Fiend now shoots Sulfuric Acid tears.
  - Imp Baby Mode is a reference to the The Babies Mod made by Zamiel, an infamous member of the Binding of Isaac community.
  - Imp Baby Mode is purely a joke option, and is meant to poke fun at how the Imp Baby (a Co-Op baby which was a reference to Fiend) shoots Sulfuric Acid tears.
  - This mode was made in retaliation after Zamiel refused to consider making cameo Co-Op babies act similarly to the characters they reference.
Fiend's Co-op character selection icon was made by _Kilburn in order to test modded character compatibility for the Co-op character selector introduced in the Repentance DLC.

Cameo Appearances

Fiend appears in the artwork of the Fiend Fire card in The Binding of Isaac: Four Souls.
A hidden Fiend appears on the cover art for G-Fuel's promotional product of The Binding of Isaac, "Isaac's Tears". The cover art was made by the Fiend Folio developer Orisghost.^[3]
Fiend appears in the game DESCENT: GOTY EDITION as a skin option for the player.^[4]

Jokes

If Fiend picks up Mercurius, white text will appear above Fiend that reads "The Winged Fiend".
- The Winged Fiend is a reference to a video made by Fiend Folio developer J.D., from before The Reheated Update released and before J.D. officially became a developer for the MOD. The video appeared to be a playthrough of J.D. playing as "Tainted Fiend" in an "early release" of The Reheated Update for the Repentance DLC. In reality, the video consisted of the Afterbirth+ edition of the MOD being played in Repentance causing bugs and issues. "Tainted Fiend" was just normal Fiend that was given Mercurius due to the prior playthrough having Eden's Blessing.^[5]
  - The video was ultimately made to poke fun at some people who were complaining about the long wait for The Reheated Update to be finished, as well as parodying those that were attempting to play the Afterbirth+ edition of Fiend Folio in Repentance and complaining about it having glitches, softlocks and crashes making it unplayable, not realizing that it was not compatible with the DLC.
If Fiend picks up Horncob, white text will appear above Fiend that reads "The Unscrupulous".
- "The Unscrupulous" is a reference to a joke Tainted Fiend teaser that the Fiend Folio developers made before The Reheated Update came out.^[6]^[7]
In the files, there exists a (unused and unfinished) spritesheet of Fiend with the appearance of Gru from the movie Despicable Me, as well a spritesheet of Fiend's Friends with the appearance of the Minions from the movie.
- Both of these were shown off in a joke announcement posted in the Fiend Folio Cornmunity Discord Server, proclaiming that Fiend has been reworked and renamed into "Nefarious Gru".^[8]
- Newly spawned Fiend Minions have a 1/100,000 chance of turning into these Despicable Me Minions.

Audio

Various sounds of Fiend getting hurt.

Sound of Fiend dying.

Gallery

For more images, see the gallery here: Fiend/Gallery

Fiend's cutscene portrait when transitioning between floors or in the versus screen of a Boss.
Fiend's "thumbs-up" gesture, depicting him "flipping the bird".
The ghost of Fiend.
Fiend's Immoral Minions, made from Immoral Hearts.
Fiend's Evil Minions, made from Black Hearts.
Fiend's Minions when Fiend has flight.
Hollow Friends, worth only half an Immoral/Black Heart.
Fiend's menu portrait.
Fiend's starting room tutorial.
Fiend's icon in the Co-Op selection menu.
Fiend's old appearance on the Boss Versus screen in Afterbirth+.
Fiend's presumed Achievements from the Afterbirth+ era. He later got unlocks in the Reheated update for Fiend Folio.
An old 3D Render of Fiend from Afterbirth+.
Picture of a familiar-looking imp found on the carton of the G-Fuel promotional product, "Isaac's Tears".
Fiend as he appears in DESCENT: GOTY EDITION.
Fiend, along with other members of Fiend's gang.
Appearance of the very rare Gru minions.