Binding of Isaac: Rebirth Wiki

Transformations alter Isaac's appearance and grant him special abilities.

A transformation occurs when obtaining at least three different items from a particular set of items.
These collectibles always share a particular theme that corresponds with the transformation.

Transformation Sets[]

ID Name Appearance Description
0 Guppy Guppy

Removed in Repentance Grants flight and spawns a Blue Fly each time a tear hits an enemy.
Added in Repentance Grants flight and adds a 50% chance to spawn a Blue Fly when a tear hits an enemy.

1 Beelzebub Beelzebub

Grants flight. Converts small enemy flies into Blue Flies. Added in Repentance Larger flies become friendly and follow Isaac between rooms.

2 Added in Afterbirth Fun Guy Fun Guy

+1 Red Heart Container.

3 Added in Afterbirth Seraphim Seraphim

Grants flight and gives +3 Soul Heart Soul Hearts.

4 Added in Afterbirth Bob Bob

Isaac leaves a trail of green poisonous creep as he walks that deals 6 damage per second.

5 Added in Afterbirth Spun Spun

Gives +2 damage and +0.15 speed, and spawns a random pill upon transformation.

6 Added in Afterbirth Yes Mother? Yes Mother?

Isaac gains a stationary knife that trails directly behind him. It synergizes like Mom's Knife Mom's Knife would.

7 Added in Afterbirth Conjoined Conjoined

Adds two tumors that fire diagonally from Isaac's head. -0.3 Damage, -0.3 Tears.

8 Added in Afterbirth Leviathan Leviathan

Grants flight and gives +2 Black Heart Black Hearts.

9 Added in Afterbirth Oh Crap Oh Crap

Whenever a pile of poop is destroyed, restores half of a red heart.

10 Added in Afterbirth † Bookworm Bookworm

Roughly 25% of the time, Isaac shoots an extra tear, like 20/20 20/20.

11 Added in Afterbirth † Adult Adult

+1 Red Heart container.

12 Added in Afterbirth † Spider Baby Spider Baby

Spawns a spider familiar that applies random status effects to enemies it comes in contact with.

13 Added in Afterbirth † Stompy None

Taking damage has a chance to spawn rock waves. Added in Repentance Isaac can break obstacles by walking over them.

n/a Added in Afterbirth Super Bum Super Bum

Replaces Bum Friend Bum Friend, Dark Bum Dark Bum, and Key Bum Key Bum with Super Bum. This bum collects any of the other beggars' pickups, and offers twice the rewards.


  • Items only need to have been acquired once in order to count.
    • Removed in Repentance Duplicate items (like those acquired from Added in AfterbirthDiplopia Diplopia) do not count toward transformations when picked up. Only the first instance of an item Isaac owns will count.
    • Added in Repentance Duplicate items are all counted.
    • Activated collectibles (e.g. Guppy's Head Guppy's Head) can be picked up once and then swapped away with another without any loss to transformation progress.
  • Removed in Repentance Rerolling items with a dice room, the D4 D4, or the D100 D100 will not remove progress towards the transformation.
    • Added in Repentance The transformation will be lost if the items required are rerolled or otherwise lost, eg. Sacrificial Altar Sacrificial Altar. Items acquired by rerolling into them do not count towards any transformations.
  • Added in Afterbirth Familiars gained from Cambion Conception Cambion Conception or Immaculate Conception Immaculate Conception do not count towards transformation progress.
  • Trinkets do not count toward progress for any transformation, with the sole exception of Added in RepentanceKid's Drawing Kid's Drawing that counts for Guppy transformation.
  • Pills only count toward Adult and Stompy, they do not count toward progress for any other transformation.
  • Characters that start with an item that counts towards a transformation do count as one of the three items needed for a transformation, such as Judas starting with The Book of Belial.
  • Familiars obtained through Soul of Lilith count towards the Conjoined transformation.
  • Added in Repentance When playing as Jacob and Esau Jacob and Esau or Tainted Lazarus Tainted Lazarus only the character that picks up an activated item first gets the progress for related transformations, however both characters in the set may undergo the same transformation if they both collect the remaining required set items left in the item pool.
  • Added in Repentance Tainted Isaac Tainted Isaac will not lose a transformation nor progress towards it if he replaces an item that counts towards that transformation.


  • Transformations can be combined, keeping the effects of all transformations with no effects overriding others.
  • Transforming into Beelzebub for the first time will unlock the Lord of the Flies achievement and Added in Afterbirth †Angry Fly Angry Fly.
  • Since none of the Afterbirth transformations unlock an achievement or item, attaining them is not required for 100% completion of the game in terms of achievements. Added in Afterbirth However, this is only true if you unlocked Mom's Contacts Mom's Contacts on Rebirth, as the Yes Mother? transformation will happen once you collect three Mom items on Afterbirth and Afterbirth †.
  • Many of the Afterbirth transformations override the charge animations of items such as Monstro's Lung Monstro's Lung and Brimstone Brimstone, potentially making them more difficult to use.
    • Added in Afterbirth † There is now an option to show a charge bar that floats above Isaac.



  • There are two transformations in the base game, nine more in the Afterbirth DLC, and four more in the Afterbirth † DLC.
  • In the original The Binding of Isaac flash game, the transformation into Guppy was the only one available, making it chronologically the first.
    • The Eternal Edition of the original The Binding of Isaac game added another transformation that turned Isaac into an angel after gaining 7 heart containers from eternal hearts.
  • Rebirth introduced Beelzebub as the chronologically second transformation.
  • The original name for the Beelzebub transformation was Lord of the Flies.
  • The reason no new transformations have been added to Repentance is because Edmund and the dev team do not like them, as they view them as significant advantages gained only from being lucky enough to find specific items. This is why Guppy, the most powerful transformation, requires much more effort to get compared to a transformation like Spider Baby. If any new transformations were to be added, they would be purely visual.[1]