Binding of Isaac: Rebirth Wiki
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(in Repentance)

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

Effects[ | ]

  • Spawns a flat, rotating fetus familiar that follows Isaac.
  • After entering a Boss RoomBoss 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 around 20% slower.
  • 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.

Notes[ | ]

  • If Vanishing Twin becomes a clone of a boss with a hardcoded item drop, such as Boss Gish ingameGish 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 VoidThe Void) or when getting Curse of the LabyrinthCurse 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 Boss Great Gideon ingameGreat Gideon, 2 extra waves of enemies are added to the battle, as well as second Great Gideon also performing attacks.
  • If Vanishing Twin turns into Boss Clutch ingameClutch, the clone will immediately enter its second phase due to not having any Clickety ClackClickety Clacks to possess.
  • When multiple Boss Rotgut ingameRotguts are spawned, only one needs to be entered.
  • In true Co-op, the pedestal spawned by vanishing twin will have an extra item for each player.
  • Familiars that follow behind Isaac have a certain priority in how close their position is to him over other familiars, with Vanishing Twin having the lowest priority at 6th and thus being farther from Isaac than familiars of different priorities.

Synergies[ | ]

  • Collectible Sacrificial Altar iconSacrificial 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.
  • Collectible Satanic Bible iconSatanic 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.
  • Collectible There's Options iconThere's Options: Will spawn an additional item choice for the item spawned by Vanishing Twin.
  • TickTick: Further lowers the health of both the original boss and its clone.
  • Collectible Vanishing Twin iconVanishing 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 Boss Great Gideon ingameGreat Gideon adds 2 extra waves of enemies.

Interactions[ | ]

  • Collectible BFFS! iconBFFS!: Will increase the fetus' size, although it has no effect after the transformation happens.
  • Collectible Box of Friends iconBox 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.

In-game footage[ | ]

Trivia[ | ]

  • 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 Boss C.H.A.D. ingameC.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.
  • Vanishing Twin used to not have the "lazarussharedglobal" tag with the lack thereof causing bugs. These bugs would occur when Character Tainted Lazarus iconTainted Lazarus used Collectible Flip iconFlip. If Flip was used after the boss was cloned, it would not drop an additional item. If Flip was used after defeating the boss and gaining the item, it would spawn another item of the current pool on the next flip.

Bugs[ | ]

Bug Bug! Some familiars like Collectible Headless Baby iconHeadless 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 EmperorIV - 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 Boss Great Gideon ingameGreat Gideon is unstable - attempting to kill a clone of Great Gideon with Chaos CardChaos Card will sometimes fail and cause a softlock.
Bug Bug! When cloning Boss Turdlet ingameTurdlet, Vanishing Twin will only clone 1 segment of the boss and will stick to it, making a 6-segments Turdlet.


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