Binding of Isaac: Rebirth Wiki

Added in Repentance

Vanishing Twin is an unlockable passive item added in The Binding of Isaac: Repentance.


  • Spawns a flat, rotating fetus familiar that follows Isaac.
  • After entering a Boss Room Boss Room, the familiar will move closer to the center of the room, and become a clone of the boss. Isaac must defeat both bosses.
    • The Vanishing Twin and original boss will be set to 75% of their maximum health, and their movements and attack patterns will be slightly slowed.
  • Upon death, the clone boss will drop an item pedestal from the boss item pool, even if the fight isn't over yet.
  • The Vanishing Twin familiar will return when Isaac reaches the next floor.


  • If Vanishing Twin becomes a clone of a boss with a hardcoded item drop, such as Gish Gish or one of the Harbingers, the second item pedestal will be from the boss item pool instead of the boss' regular drop.
  • Managing to defeat the boss before the twin has transformed into it will not prevent the twin from doing the transformation, and the boss fight will continue.
  • Obtaining Vanishing Twin in the boss fight itself will not take effect immediately. The boss room must be re-entered in order for the twin to transform.
  • On floors with multiple bosses (e.g. The Void The Void) or when getting Curse of the Labyrinth.png Curse of the Labyrinth, the twin will only act on the first boss encountered.
  • The twin will not transform into bosses that are randomly found in some default room layouts.
  • This item has no effect in Greed Mode and will not normally spawn in this game mode.
  • If it becomes a clone of Great Gideon Great Gideon, 2 extra waves of enemies are added to the battle.


  • Sacrificial Altar Sacrificial Altar: The twin can be sacrificed normally at any time.
    • If sacrificed after it's transformed into a boss, it will still give an item from the sacrifice, but the boss will not disappear and will also not spawn an additional item.
  • Satanic Bible Satanic Bible: Using it before killing the clone boss will cause it to spawn an item from the Devil Room item pool instead of from the Boss item pool. This item must be purchased just like a normal Devil Deal.
  • There's Options There's Options: Will spawn an additional item choice for the item spawned by Vanishing Twin.
  • Tick Tick: Further lowers the health of both the original boss and its clone.
  • Vanishing Twin Vanishing Twin: Picking up multiple copies of the item will result in multiple clones getting spawned.
    • Each boss will have its health reduced down further to 75% of the health of its previous clone.
    • Each of the bosses will spawn a separate item.
    • Each clone of Great Gideon Great Gideon adds 2 extra waves of enemies.


  • BFFS! BFFS!: Will increase the fetus' size, although it has no effect after the transformation happens.
  • Box of Friends Box of Friends: No effect.
  • IV - The Emperor? IV - The Emperor?: The twin will clone the additional boss and spawn an item if the original one has not been visited yet. However, this will not allow for another item to be obtained from the floor's original boss, because the twin won't be active until the next floor.
  • If Tainted Lazarus Tainted Lazarus has used Flip Flip after the boss has been cloned, it will not drop an additional item.
    • After defeating the boss and gaining the item, it may spawn another item of the current pool on the next flip.
  • In true Co-op, the pedestal spawned by vanishing twin will have an extra item for each player.

In-game footage[]


  • A Vanishing Twin is a fetus that dies during gestation and is reabsorbed by its twin, hence the appearance of the item.
    • The familiar's flat appearance is due to a real life phenomenon known as fetus papyracaeus, where instead of a vanishing twin being physically reabsorbed by the other, the body stays in the womb and gets crushed and flattened by the healthy twin in full term between the fetus' expanding membranes and the uterine walls.
  • When encountering C.H.A.D. C.H.A.D., the original will notably shrink once its clone spawns, due to Vanishing Twin reducing its HP and C.H.A.D.'s HP being linked to its size.


Bug Bug! Some familiars like Headless Baby Headless Baby will follow the other boss as if it was a familiar.
  • After beating the boss, familiars that were after Vanishing Twin will get bugged and stay at the entrance of every room instead of following the player.
Bug Bug! Using IV - The Emperor IV - The Emperor while in a boss fight will immediately kill the twin boss and spawn the second item for free; the player will only have to fight one boss thereafter.
Bug Bug! In Double Trouble boss fights, only one of the bosses will get copied, but both of them will get their health lowered down to 75%.
Bug Bug! The interaction between this item and Great Gideon Great Gideon is unstable - attempting to kill a clone of Great Gideon with Chaos Card Chaos Card will sometimes fail and cause a softlock.
Bug Bug! When cloning Turdlet Turdlet, Vanishing Twin will only clone 1 segment of the boss and will stick to it, making a 6-segments Turdlet.