Vanilla Tweaks

While the majority of content in Fiend Folio only adds new features to the game without modifying some of the existing gameplay mechanics of The Binding of Isaac: Repentance, there is a still a large handful of exceptions that expand some existing elements, and drastically change the feel of the game.

Stage Additions

The stages are more alive than ever! From discovering prehistoric caves to exploring abandoned sewer plants, Fiend Folio adds new backdrops and changes to each floor to solidify their theme and feeling.

• Main Article: Stage Additions

Poop Spells

Tainted ??? can now use new varieties of poop with Fiend Folio: Reheated, some of them utilizing the MOD's own unique Poop obstacles.

Name	Icon	Appearance	Effect
Shampoo			When thrown, slides along the ground, leaving behind a trail of blue creep which deals 2 damage per tick. Can be picked up again after being thrown.
Cursed Poop			Has a purple aura around itself which applies fear to nearby enemies.
Evil Poop			Has a dark aura around itself which makes enemies inside of it take increased damage.
Fuzzy Poop			Passively spawns up to 3 Blue Skuzzes in the room.
Dip		N/A	Turns all nearby Poops into their respective Dip familiars.

Pill Colors

Fiend Folio: Reheated also added new pill colors to memorize! These have a chance of appearing in place of the regular vanilla pill colors encountered.

Note: These new pill colors are purely cosmetic; they do not correlate to the types of possible pill effects, nor number of pill effects that appear in the pill pool, which will always remain at 13 per run.

Pill Colors

For the new pills and their effects added in Fiend Folio, see Pills.

Vanilla Enemy Changes

Besides adding new enemies, Fiend Folio also modifies and improves a few existing ones. These modifications can be toggled in the Dead Sea Scrolls menu of the MOD.

Dank Squirt

Dank Squirts will no longer split into two Clots. Instead, they will spawn several Blots along with a small shower of tar projectiles, and leaving behind a puddle of slowing black creep.

Swinger

If the base of a Swinger is killed, it will spawn a Maw with a unique appearance that looks identical to the Swinger's head.

Blue Conjoined Fatty

Blue Conjoined Fatties have a unique appearance when encountered in The Chest, resembling the character ??? instead of Hush.

Hosts

Hosts spawned from Skulls will have a different appearance, depending on the floor or room type.

All these Hosts also have unique Red Host appearances when their skull is removed by Mom's Bracelet.

• 

  Depths Host.

• 

  Necropolis Host.

• 

  Dank Depths Host.

• 

  Mausoleum Host.

• 

  Mausoleum Host, after Mom's Heart has been killed.

• 

  Gehenna Host.

• 

  Sheol Host.

• 

  The Siren's skull Host.

Lil Portal

Lil Portals are now able to spawn some of the following insects added in Fiend Folio:

• Shot Fly
• Shoter
• Skuzz
• Beeter
• Spitroast
• Mayfly
• Lightning Fly

Lil Portals will also have a unique skin if encountered in Gehenna, giving them a red appearance.

Waiting Enemies

Several of Fiend Folio's foes, along with a plethora of vanilla enemies, have received a special "waiting" variant.

Waiting enemies will not spawn immediately when Isaac enters the room, but only after all other enemies have been defeated. Each enemy has their own way of appearing in the battlefield, such as burrowing enemies appearing from beneath Isaac's feet, leaping enemies falling from off-screen, or spider enemies rappelling down from the ceiling with spider silk!

• If Isaac is standing in the same spot where an enemy would appear, it will wait until Isaac moves out of the way before doing so.

Boss Rush

As well as adding new bosses, Fiend Folio also expands Boss Rush by adding some of its new bosses, as well as including some that were missing from the vanilla game!

The following bosses in Fiend Folio have been added to Boss Rush:

• Buck
• Honeydrop
• Buster
• Griddle Horn
• Battie
• Kingpin
• Pollution

Fiend Folio bosses will not be champions during a champion Boss Rush.

The following bosses from the vanilla game have been added to Boss Rush:

• Baby Plum
• Rag Mega
• Big Horn
• Bumbino
• Sisters Vis
• The Pile
• Reap Creep
• Lokii
• Teratoma
• Daddy Long Legs
• Triachnid

Delirium

Delirium is able to transform into a handful of the bosses added in Fiend Folio if they were previously encountered in the run. They will even have unique skins when doing so.

The following bosses Delirium can transform into are:

• Buck
• Honeydrop
• Griddle Horn
• Battie

Notes

• In the files, there is a Delirium skin for Kingpin, though it seems to be unused.

Miscellaneous

Rune of Berkano

Rune of Berkano has received a small buff, as now it also spawns three Blue Skuzzes in addition to the 3 Blue Flies and Blue Spiders.

Boom!

Added an explosion sound effect when picking up Boom!, a trait which has also been given to all other X10 items.