The Womb is the fourth environment of the game. The player will enter it after killing Mom, but only after they have beaten her once before. It is possible to access the Womb before even killing Mom once, by digging down from Depths II using the We Need To Go Deeper! item. The enemies in this enviroment are mainly worms and other medical things, and their behaviour often involves disappearing and reappearing across the room (i.e. with the Baby's teleporting or the burrowing behaviour of Para-Bites, Lumps and Fred)
From the chapter The Womb/Utero and onwards, all damage done to Isaac is set to 1 Heart ( ). Any type of damage that does 1 heart of damage by default (e.g Bombs) will still do 1 heart of damage in The Womb/Utero and onwards. The only way to avoid it is to use The Wafer item, which sets every type of damage to 1/2 Heart ( ).
- 1: The room will always appear once in this floor
- 2: The room will always appear twice in this floor
- Possible: There is a chance for this room to appear, usually due to certain criteria being met
- -: The room cannot appear in this floor.
|Rooms with the core game|
|Rooms||The Womb 1||The Womb 2||The Womb XL||Note|
|Regular Rooms||22 - 26||22 - 26||39 - 40||The player must have Wrath of the Lamb installed for The Womb XL to appear.|
|Treasure Room||-||-||-||From The Womb/Utero and onwards, no more Treasure Rooms will appear.|
|Shop||-||-||-||From The Womb/Utero and onwards, no more Shops will appear.|
|Boss Room||1||1||2||Boss Rooms are always linked in XL floors.|
|Challenge Room||Possible||Possible||Possible||Will only be generated if Isaac has full health while entering the floor.|
|Arcade||-||Possible||Possible||Only generated when Isaac has 5 Coins upon entering a new floor or part.|
|Devil Room||Possible||Possible||Possible||If the Devil Room is entered at The Womb 2/The Womb XL, there will be a trapdoor leading to Sheol instead of items being sold for Heart Containers. The trapdoor appears even if the player has not killed It Lives!.|
|I AM ERROR||Possible||Possible||Possible||Only reachable by using the Telepills, which have a 6.66% chance to teleport Isaac to this room.|
|Rooms with Wrath of the Lamb|
|Rooms||The Womb 1||The Womb 2||The Womb XL||Note|
|Super Secret Room||1||1||1|
|Angel Room||Possible||Possible||Possible||If the Angel Room is entered at The Womb 2/The Womb XL, there will be a trapdoor leading to Sheol instead of an item at a pedestal. The trapdoor appears even if the player has not killed It Lives!.|
|Library||Possible||Possible||Possible||5% base chance to spawn, 25% if Isaac is holding a book.|
|Boss Challenge Room||Possible||Possible||Possible|
| Sucker||Flies slowly towards Isaac, exploding into 4 projectiles in a + formation upon death.|
| Boil||Stationary enemy that shrinks upon being hit. Will quickly swell up if not killed in time. Fires multiple short-ranged blood projectiles when fully swollen.|
| Globin||Walks towards Isaac, dealing one heart of contact damage. Turns into a pile of goo after taking enough damage, where it can be killed. Will regenerate after a short amount of time if not killed quickly.|
| Gazing Globin||Quickly walks towards Isaac, dealing one heart of contact damage. Turns into a pile of goo and slides away after taking enough damage, where it can be killed. Will regenerate after a short amount of time if not killed quickly.|
| Brain||Crawls around the room, leaving a trail of red Creep that does one heart of damage.|
| MemBrain||Slowly moves around the room, occassionally hopping and firing 8 large blood shots in all directions. Will split into 2 Brains upon death.|
| Guts||Attaches itself to a wall or obstacle, such as a Rock, rolling around the room.|
| Para-Bite||Moves towards Isaac. Can burrow underground and reappear elsewhere.|
| Fred||Fires an IPECAC shot at Isaac. Will hop out of the ground and burrow elsewhere, firing 4 blood shots in an X pattern while doing so.|
| Lump||Fires 3 fast-moving blood shots at Isaac when he gets in its line of sight. Will burrow underground and reappear elsewhere after firing its shots.|
| Leech||Quickly charges towards Isaac when he gets in its line of sight.|
| Kamikaze Leech||Quickly charges towards Isaac when he gets in its line of sight. Explodes with a large blast radius upon death.|
| Host||Invulnerable stationary enemy. Raises its head up when Isaac gets close, revealing a fleshy stem that can be damaged. Upon raising its head, it will fire 3 blood shots and lower its head again.|
| Red Host||Stationary enemy that can be damaged even when its head is lowered. Fires 5 blood shots instead of 3 when rising, and fires more frequently.|
| Vis||Charges up a Brimstone laser when Isaac gets in its line of sight.|
| Chubber||Fires a Little Chubby-like familiar that deals one heart of damage when Isaac gets in its line of sight.||✔|
| Eye||Quickly fires a Technology-like laser at Isaac.|
| Bloodshot Eye||Quickly fires a Brimstone-like laser at Isaac.|
| Dople||Copies Isaac's movements, and fires tears at the same time as him.|
| Evil Twin||Copies Isaac's movements, and fires tears at the same time as him.|
| Baby||Fires a single blood shot at Isaac. Can teleport and reappear elsewhere.|
| Angelic Baby||Fires 3 blood shots at once at Isaac, has much more health than regular Babies.||✔|
|Minibosses (7 Sins) found in normal rooms:|
|Wrath||Usually paired with another Wrath. Fires Bombs at Isaac that detonate after a short amount of time, in a manner similar to Dr. Fetus.|
|Sloth||Usually paired with another Sloth. Fires IPECAC shots at Isaac, while occasionally spawning Chargers|
|Envy||Usually paired with another Envy. Moves around the room slowly at first, and then splits into two faster-moving heads after taking enough damage. These heads will split into two more heads with a smaller size and increased speed after taking enough damage, which will then split into the smallest heads that do not split.|
|Lust||Usually paired with another Lust. Moves around the room quickly around the room towards Isaac.|
|Gluttony||Usually paired with another Gluttony. He has two attacks, an 8-way blood shot and a blood beam attack, similar to that used by Vis.|
|Bosses found in normal rooms:|
| Blastocyst||Hops around the room, firing 4 large blood shots in a + pattern. Splits into two smaller parts upon taking enough damage, and into an Embyro at the end.|
| Larry Jr.||Multi-segmented enemy that quickly crawls around the room, not targeting Isaac. Constantly leaves trails of Poop.|
|Monstro||Hops towards Isaac. Fires a large volley of blood shots when near Isaac. Can jump high into the ceiling and land somewhere else.|
|Duke of Flies||Floats around the room, spawning Flies. Spawns multiple Attack Flies and Pooters upon death.|
|Gemini||Two joined twins that compose 50% of the health bar each. The large twin runs towards Isaac, while the smaller twin fires fast-moving blood shots. The smaller twin will stop firing blood shots upon the larger twin's death, and instead start chasing Isaac.|
| Fistula||Floats around the room diagonally, splitting into smaller, faster versions every time it takes damage. Smallest versions spawn a Charger when killed.|
| Chub||Moves around the room randomly, charging at Isaac if he gets in her line of sight. Constantly spawns Chargers .|
|Loki||Constantly fires 4 blood shots in a plus or cross pattern, and sometimes in all 8 directions at once. Occasionally teleports around the room. Can spawn Boom Flies .|
|Peep||Slowly moves around the room, firing 6 urine shots in all directions. Can jump towards the ceiling and drop down elsewhere, like Monstro. Can release yellow Creep occasionally. Upon reaching 66% and 33% health respectively, an invulnerable eye will pop out that flies around the room diagonally like Boom Flies.|
Differences from previous floors
- Blood donation machines take away a whole heart instead of half. They can still be used twice for one heart by quickly using them again during Isaac's invincibility period after taking damage. This can be done because taking a full heart of damage gives Isaac a longer invincibility period.
- Two of Seven Deadly Sins can be encountered in one room multiple times.
"Judas' Fez" - Complete The Womb 2 once.
"The Noose" - Complete The Womb 2 two times.
"The Nail" - Complete The Womb 2 three times.
"The Quarter" - Complete The Womb 2 four times.
"The Fetus" - Complete The Womb 2 five times.
"Everything's Terrible!" - Complete The Womb 2 six times.
"The Wafer" - Complete The Womb 2 seven times.
"Money = Power" - Complete The Womb 2 eight times.
"It Lives!" - Complete The Womb 2 nine times.
"???" - Complete The Womb 2 ten times.
"Mama's Boy" - Complete The Womb without taking damage.