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

Name Appearance Description
Beelzebub Transformation Beelzebub appearance.png

Grants flight and converts small enemy flies into Blue Flies.

Guppy Transformation Guppy appearance.png

Grants flight and spawns a Blue Fly Dlc nr indicator.png each time ( Dlc r indicator.png 50% of the time) a tear hits an enemy.

Dlc a indicator.png Bob Transformation Bob appearance.png

Isaac gains a green trail of poisonous creep.

Dlc a indicator.png Conjoined Transformation Conjoined appearance.png

When attacking, the tumor faces shoot tears diagonally outwards, similar to the effect of Dlc a indicator.png Collectible The Wiz icon.png The Wiz. Also gives -0.3 damage and slightly decreases tears.

Dlc a indicator.png Fun Guy Transformation Fun Guy appearance.png

+1 Red Heart container.

Dlc a indicator.png Leviathan Transformation Leviathan appearance.png

Grants flight and gives +2 black hearts.

Dlc a indicator.png Oh Crap Transformation Oh Crap appearance.png

Whenever a pile of poop is destroyed, health is replenished by half a heart.

Dlc a indicator.png Seraphim Transformation Seraphim appearance.png

Grants flight and gives +3 soul hearts.

Dlc a indicator.png Spun Transformation Spun appearance.png

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

Dlc a indicator.png Super Bum Transformation Super Bum appearance.png

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

Dlc a indicator.png Yes Mother? Transformation Yes Mother? appearance.png

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

Dlc a† indicator.png Adult Transformation Adult appearance.png

Grants a heart container.

Dlc a† indicator.png Bookworm Transformation Bookworm appearance.png

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

Dlc a† indicator.png Spider Baby Transformation Spider Baby appearance.png

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

Dlc a† indicator.png Stompy None

Taking damage has a chance to spawn rock waves.


  • Items only need to have been acquired once in order to count.
    • Dlc nr indicator.png Duplicate items (like those acquired from Dlc a indicator.png Collectible Diplopia icon.png Diplopia) do not count toward transformations when picked up. Only the first instance of an item Isaac owns will count.
    • Dlc r indicator.png Duplicate items are all counted.
    • Activated collectibles (e.g. Collectible Guppy's Head icon.png Guppy's Head) can be picked up once and then swapped away with another without any loss to transformation progress.
  • Dlc nr indicator.png Rerolling items with a dice room, the Collectible D4 icon.png D4, or the Collectible D100 icon.png D100 will not remove progress towards the transformation.
    • Dlc r indicator.png The transformation will be lost if the items required are rerolled or otherwise lost, eg. Collectible Sacrificial Altar icon.png Sacrificial Altar.
  • Dlc a indicator.png Familiars gained from Collectible Cambion Conception icon.png Cambion Conception or Collectible Immaculate Conception icon.png Immaculate Conception do not count towards transformation progress.
  • Trinkets do not count toward progress for any transformation, with the sole exception of Dlc r indicator.png Trinket Kid's Drawing icon.png 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.
  • Dlc r indicator.png When playing as Character Jacob and Esau icon.png Jacob and Esau or Character Tainted Lazarus icon.png 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.
  • Dlc r indicator.png Character Tainted Isaac icon.png 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 Dlc a† indicator.png Collectible Angry Fly icon.png 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. Dlc a indicator.png However, this is only true if you unlocked Collectible Mom's Contacts icon.png 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 Collectible Monstro's Lung icon.png Monstro's Lung and Collectible Brimstone icon.png Brimstone, potentially making them more difficult to use.
    • Dlc a† indicator.png 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. If any new transformations were to be added, they would be purely visual.[1]

SmallIsaac.png The Binding of Isaac: Rebirth SmallIsaac.png
MainPageAchievements.png Achievements MainPageAttributes.png Attributes MainPageBosses.png Bosses TarotCard.png Cards and Runes MainPageChallenges.png Challenges MainPageChapters.png Chapters
Character Isaac appearance.png Characters MainPageBabies.png Co-op MainPageItems Small.png Items Collectible Isaac's Tears icon.png Item pools MainPageMonsters.png Monsters MainPageObjects.png Objects
Red Heart.png Pickups BlueBlue.png Pills MainPageRooms.png Rooms MainPageSeeds2.png Seeds Transformation Guppy appearance.png Transformations Trinket The Left Hand icon.png Trinkets
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