Cut Content refers to entities, mechanics, objects, graphics, etc that didn't make it into the final game but are still present within the game's data.
Pressure plates can be found in the game files and could have served as another type of obstacle. They are fully functional and can do the following things:
Nothing
Spawn a random chest
Spawn 6 Attack Flies
Spawn 6 Troll Bombs
Activate Curse of Darkness for the rest of the floor
Spawn a random pickup
Spawn 15 random coins
Buttons appear in rooms.
Various Half Hearts
Half Soul Heart and Black Heart pickups are in the game files, but they cannot be found in-game.
Half Soul Hearts are an unlockable pickup.
Colored Destructibles
There are several colored versions of certain destructibles, which could have served a purpose similar to tinted rocks.
A boss version of the Vis enemy that could have appeared in Sheol. According to the unused corresponding achievement file, Sisters Vis would have been unlocked by beating Sheol 10 times. The Sisters Vis were also a boss in Gish, one of Edmund McMillen's previous games.
This boss can be encountered, but can appear in all environments of Chapter 3, The Utero, the Scarred Womb and requires unlocking - "defeat ??? as 6 different characters"
Unused 12 Room Charge
By editing the game's "items.xml" file and setting an item to maxcharges=12, it's possible to see the charge bar in-game.
The bar is used for the Mega Blast item, which has a 12-room charge.
The bar is also used for the Delirious and Eden's Soul items, which have 12-room charges.
Breath of Life Animation
Unused Jar Charges
Unused Floors
By disabling the invalid seed check, and using an invalid seed, you can continue the game after The Chest and Dark Room, up to an additional 14 floors. They use pre-existing graphics and the same layout.
Mega Satan's Skeleton Hand
Originally, a skeletal version of Mega Satan's hands would have appeared for his 2nd form. Even if Mega Satan's hands were not killed, fully depleting his head's health in his 1st form will cause the hands to immediately despawn.
Cut Afterbirth Content
Old Man Keeper
Old Man Keeper was originally a second new playable character before ending up replaced by Keeper. This character, however, is playable since the DLC's initial release by using the Cheat Engine until in the later update patches, but he appears invisible with no sprites and has zero hearts.
On April Fool's Day since 2016, Keeper will be replaced by Old Man Keeper during the daily run for a day.
Skinless Hush
From the files, there was an unfinished sprite sheet of Hush's flayed form. At first, Edmund states that the file is a "red herring to the data miners".[1] However, this scrapped form was later confirmed to be actually intentional.[2][3]
Beta Ultra Greed
Ultra Greed, based on his unused sprite sheet, was originally featured with a beard, along with a single tooth and a rather stout-looking body build. This old Ultra Greed design supposedly represents Tyrone Rodriguez,[4] similar to Ultra Pride who also represents Edmund McMillen and Florian Himsl.
Cut Afterbirth † Content
Ultra Greedier's Hanged Sprite
Strangely, Ultra Greedier has an unused hanging sprite like his original form but appears unfinished.
Big Horn's Large Bombs
This unused bomb sprite reveals that Big Horn was intended to summon a larger bomb.
Cut Repentance Content
Dogma's Unused Attacks
There are 2 attacks that appear in the files and can be spawned using console commands, but neither are ever seen ingame normally. Due to their IDs and names, it's implied that they are unused attacks that Dogma would have used.
Entity 950.10 is "Dogma Angel Baby". When spawned, it floats around for a few seconds before charging at Isaac and exploding. Sprite sheets for these exist in the game files, which means that they may be properly implemented at a later date.
Sprites for Dogma's unused Angel Baby attack.
Entity 1000.171 is "Dogma Blackhole". When spawned, it take a moment to charge up before creating a very strong suction force, pulling in damaging tears. If Isaac makes contact with the blackhole he will take damage. The blackhole explodes into a shower of tears after a few seconds of suction.
Unimplemented Bosses
Files for several bosses created for The Binding of Isaac: Repentance that were ultimately cut can be found within the game files. However, it was confirmed that some of the bosses may have a chance to be implemented in the DLC's future updates.[5]
Maid in the Mist, a scrapped ghost-like boss. She appears to be an early version of Min-Min as the two share a Willo theme:
Clutch/The Possessor, a poltergeist-like boss. It can be spawned with the console and even has rooms, but it is not assigned to any boss pools, thus it can never appear in-game without mods. It is possibly intended for the Ashpit because of the use of Clickety Clacks. This boss is referred to in multiple different ways - its boss room is named The Possessor, but it is referred to the "bossportraits.xml" file as "Clutch". It does not have a boss title.
Raglich, a boss that appears to be a part of the Rag Man lineage. Raglich does not appear in any rooms, meaning it must be spawned with the console.
Cadavra, a pair of bosses similar in appearance to Chimera. Their walking animation gifs were first leaked by Edmund McMillen on September 4, 2020[6] but they were never found in the DLC's final release. Unlike the previous two bosses, Cadavra does not exist as an entity and cannot be spawned in-game. It does not have a portrait nor a boss title. Edmund stated that they're "still in pieces maybe one day", [7] implying that Cadavra would be later added in the future update patches some other time.
Tainted Mr. Maw, an enemy resembling three Maw faces stuck together. The enemy's sheet suggests that each face broke off as its health lowered.
Sprites for the unused enemy Tainted Mr. Maw.
A variant of Drips themed after Turdlet, likely meant to be a part of Turdlet's fight.
Golden Henry, an extremely rare variant of the Henry enemy that would appear golden in appearance. According to one of the playtesters the enemy was scrapped due to Henry already being exceedingly rare as is.File:Golden Henry.png
Sprites for the unused enemy Golden Henry.
Split Rage Creep, an enemy resembling Rage Creeps, but with a more gored body.
Ragcreep, an unspawnable type of Creep which spits homing shots, spawned as part of Raglich's fight.
Unimplemented Items
Unused files for items exist within the game's files.
Beth's Heart, a passive item that would summon a blue heart familiar. It is unknown what this familiar would have done.
Blank Bombs, a passive bomb upgrade that would be able to destroy nearby enemy projectiles.
Unimplemented Pickups
Several unused achievements for pickups exist.
Illusion Hearts
Rune of Ingwaz
Rune of Sowilo
Unimplemented Challenges
Several unused achievements exist that mention the following challenges being unlocked. It is unknown what the challenges would have had.
Ghost Babel
Dimension Red
Divide and Conquer
Unimplemented Co-op Babies
Several unused achievements exist for co-op babies that never made it in.
BFF Baby
Duplex Baby
Lot Baby
Pawn Baby
Salty Baby
Mortis
An unused floor which would have been an alternative version of Corpse exists as two empty room files with no associated assets. In the music xml there is also a listing labeled as "not done" after Gehenna which uses the womb tracks as placeholder.
Curse of the Giant
A new curse from the Antibirth mod, which generates a floor with special big rooms made from combining multiple small rooms together, remains in the game files in Repentance, but as of yet cannot be encountered in-game.
Derpy Plum
Next to Baby Plum's animation file is a file called "908.000_derpy plum.anm2" which is missing its associated sprite sheet. There are two images of what appears to be Derpy Plum, as shared by one of the developers.
Cut Antibirth Content
Cut Characters
Edith - An unused character from Antibirth that could only move through teleporting. It was confirmed early on by Ed that Edith would not be added, however, a statue that looks similar to Edith does appear rarely when using VII - The Chariot?. In addition, the Tainted version of The Forgotten has a similar mechanic and appearance to Edith.
Cut Items
1012 - Book of Despair - An active item that would have granted a temporary tears up on use.
1034 - Menorah - This is the unused item ID of 587.
1067 - Voodoo Pin - Is the same thing as the Dull Razor (which was implemented in Afterbirth+). This is the unused item ID of 620.
1075 - Knife Piece 3 - There are only two Knife Pieces now.
1080 - Stone Bombs - This item would have made Isaac's bombs leave rock waves on explosion.
613 - Salt Shaker - Was Edith's active item. Edith was a planned character for Antibirth, but it was cut out for gameplay reasons. (It was item ID 613 but now this ID is currently unused.)
630 - Lucky Seven - Was an item planned for the first Antibirth update. (It was item ID 630 but now this ID is currently unused.)
648 - Pill Crusher - Was an item planned for the first Antibirth update. (It was item ID 648 but now this ID is currently unused.)
??? - Donkey Jawbone - This item was scrapped, but exists as Tainted Samson's gimmick. It's unlock was replaced by Bloody Gust.
Cut Monsters
Some monsters from the Antibirth mod are found in the game files but unused, while others are completly absent in Repentance.
It is possible to encounter these enemies along with other cut enemies with TMTRAINER or in the DELETE THIS challenge, although it is highly unlikely.[8]
Unused monsters:
Blind Bat - A variant of One Tooth. Starts out asleep. When Isaac gets close, it wakes up and chases Isaac, followed by a group of three more Blind Bats.
Echo Bat - A variant of One Tooth. Flies towards Isaac and periodically fires three white orbs. If an orb hits Isaac, he becomes confused and his movement is reversed for a few seconds.
Corpse Eater - Rapidly moves around the room erratically and charges at Isaac if he comes within its line of sight. When spawned in game, it will behave like normal but only has the front end for it's sprite.
Carrion Rider - A variant of Corpse Eater. Rapidly moves around the room erratically and charges at Isaac if he comes within its line of sight. The Bony on its back shoots at Isaac.
Exorcist - Summons ghost enemies such as Wizoobs, Lil' Haunts, and Candlers.
Necromancer - Summons skeleton enemies such as Bonies and Big Bonies.
Nightwatch - Invulnerable enemies. Moves in a fixed pattern or rotates in a spot. If Isaac enters its light, it will lock all doors, summon enemies, and vanish.
Swapper - A variant of Baby. Slowly floats towards Isaac and fires purple lasers. Occasionally teleports and reappears elsewhere. Has a chance to swap positions with Isaac.
Strifer - Walks horizontally or vertically, attempting to line up with Isaac. Frequently fires lines of four tears forwards.
Barfy - A variant of Fatty. Wanders around the room, and slowly follows Isaac when he's in its line of sight. Occasionally spews clusters of green shots that leaves green creep towards Isaac.
Vessel - A variant of Fatty. Walks around the room and explodes into Small Maggots upon death.
Unnamed Gaper - An unnamed gaper with what seems to be melting flesh on the side of it's face can be found in the files, though it doesn't seem to have any behavior as of yet.
Removed monsters:
Dumpling - Flies around and farts if Isaac is close, if it is damaged, and when it dies. Farts knock Isaac back and propel it forwards.
Skinling - A variant of Dumpling. Their behavior is similar but their farts are poisonous.
Scab - A variant of Dumpling. Flies towards Isaac. Upon death, farts and sends out 6 blood shots in all directions.
Fissure - A Dumpling/Trite hybrid. Jumps towards Isaac like a Trite. When it jumps, it fires a red shot towards Isaac. Occasionally, it stands still and spews a chaotic burst of red shots.
Screamer - Walks slowly around the room. If Isaac gets too close, it will scream, paralyzing Isaac. It will gain a slowing aura and start charging towards him.
Coil - Creates beams of electricity to other enemies in the room. Touching the electricity damages Isaac. Cannot be killed.
Stillborn - Slowly floats towards Isaac, occasionally firing blood shots. Cannot be killed and dies when the room is cleared.
As well, there is a cut Orange-Red champion that behaved similar to the flashing green champion, splitting once, and then having its clones split.
Cut Pickups
Rune of Kenaz - Poisons all enemies in the room for 48 hits. Seems to do between 1.0 and 3.5 damage per hit, but never scales off of Isaac's damage stat.
Rune of Othala - Gives Isaac a random item that he already holds. Items interact like how they would if you had gotten them from a pedestal.
Rune of Gebo- Interacts with any machine or beggar in the room. Donates 7 coins to donation machines, plays beggars 6 times, plays blood machines 4 times, plays other machines 5 times. Machines and beggars have an increased chance to pay out or explode, even paying out at only one play.
Rune of Fehu - Turns all pickups or items in the room into coins. Coins generated are equal to how much the item would be worth in a shop (Items give 15 cents, trinkets give 5 cents, black hearts give 6 cents, 1+1 bombs/keys give 10 cents). Does not work on chests, open or closed, unless the chest has a pedestal item. Does not work with pickups or items not on the ground (Shop items, Devil deals).
This effect has been implemented in the form of the Hermit? inverted tarot card.
Immortal Hearts - Take two hits to be fully depleted and will regenerate from half to full upon clearing a room.
Cut Obstacles
Red TNT - Red TNT barrels explode when destroyed. Unlike regular TNT barrels, red TNT only needs to be shot once to be detonated. They also detonate if Isaac or an enemy walks into it.
Corpse Polyps- Originally, Polyps in Corpse where meant to behave different when destroyed, having their own drops. This was scrapped in Repentance and they now behave like normal polyps.
Cut Challenges
Turbo!: Starts the game with Cain. The game is significantly sped up.
Buttons appear in rooms.
Half Soul Hearts are an unlockable pickup.
Marked Skulls are an unlockable obstacle.
This boss can be encountered, but can appear in all environments of Chapter 3, 
The Binding of Isaac: Rebirth
