This article is about the playable character. For other uses, see ??? (Disambiguation).
???, also known as the Blue Baby, is a character unlocked by defeating 
Mom's Heart ten times. He starts with three 
Soul Hearts, and his health meter is unique in that he cannot gain red heart containers. If an item would grant him a red heart container (including an empty one), it adds a Soul Heart instead. While he has no passive starting items, he does spawn in with 
The Poop.
Notes[ | ]
- Sleeping on a bed will give ??? three
Soul Hearts. - Enemies who deal full hearts of damage can be very dangerous in the early floors of the game.
- The Poop - While not the most useful item - can allow ??? to cross small gaps by bombing the Poop from the opposite side, much like one would for Rocks. Furthermore, in rooms with non-flying enemies that chase the player (except Spiders), the poop can be used in a corner of the room, making ??? untouchable and allowing the player to kill them without taking damage (if the player moves away from the pile of Poop generated, this will no longer work).
- Bone Hearts grant an empty Bone Heart upon pickup, but they cannot be refilled using Red Hearts.
- The amount of Soul Hearts it costs to purchase an item in Devil Room deals is equal to its Red Heart container cost, unlike other characters with no red health for whom it will always cost 3 soul hearts.
- ??? has an innate Lil Larva effect; destroying a poop while playing as him will spawn a Blue Fly.
- A possibly unintended effect is that this stacks multiple ???'s in true coop. This means that, along with The Poop, the potential flies gained per room increases quadratically with players, with the formula simply being the amount of ???'s in game to the second power.
Item Interactions[ | ]
Positive[ | ]
- Abaddon costs three Soul Hearts and grants six Black Hearts, damage up, fear shot, and no negative effects to ???. Abaddon can be bought safely regardless of current health, because its price can be deducted from the acquired Black Hearts retroactively.
- Abaddon will give 2 black hearts on pickup, essentially refunding the cost to obtain the item from a Devil Room.
- D20 and GB Bug can be used to reroll any red hearts that may drop into useful pickups.
- Ankh is effectively a 1up! for ???.
- Athame can be used to produce black hearts upon taking damage.
- Balls of Steel pills or V - The Hierophant grant two soul hearts, both of which are more useful than normal HP up items.
- The Rune of Dagaz grants one soul heart as well as lifting any curses.
- The XI - Strength card gives ??? a permanent soul heart.
- Book of Revelations grants ??? soul hearts.
- Ceremonial Robes costs three two Soul Hearts and grants three Black Hearts and damage up. Like Abaddon, this item is always safe to take.
- Crown Of Light will always activate when entering a room, but still deactivates after taking damage.
- Mitre and Daemon's Tail replace useless Red Hearts with Soul and Black Hearts respectively.
- Dark Bum converts useless Red Hearts into Black Hearts and blue spiders.
- Dark Bum can now also drop pills, cards, and runes, which can include V - The Hierophant, Balls of Steel, or Rune of Dagaz.
- Dead Cat will set Soul Hearts to 1, but can be used to gain devil deals by sacrificing the extra lives.
- Dim Bulb is able to be activated every room due to the single charge on The Poop, providing a consistent stat boost.
- Empty Vessel will always be active. Additionally, it costs 1 Soul Heart and returns 2 Black Hearts, so the item is always safe to take.
- Gimpy has a chance to spawn Soul Hearts when hit.
- Hallowed Ground turns all The Poop uses into holy poops.
- Lazarus' Rags causes ??? to be resurrected as Lazarus Risen when he dies, allowing the gathering of heart containers. Once this happens, however, you are no longer playing as ???, and therefore cannot get any of his achievements/unlocks. The same effect happens with the use of Judas' Shadow.
- Maw Of The Void can produce Black Hearts.
- Midas' Touch makes The Poop create Golden Poop.
- Monkey Paw will drop 3 Black Hearts when at half a heart, but must take damage for each one to spawn.
- Petrified Poop is useful early on to get more pickups from The Poop every room.
- The Polaroid and The Negative will always activate when taking damage.
- The Relic, which is generally useful, is especially useful to ??? as it spawns Soul Hearts.
- Satanic Bible generates Black Hearts.
- Using Satanic Bible now also causes boss items to turn into devil deals that cost hearts, which is often worth since Devil deal items are cheap and better than boss items.
- Serpent's Kiss can produce Black Hearts by poisoning enemies.
- Serpent's Kiss now only produces Black Hearts from contact damage poison, making it slightly less useful for ???.
- Squeezy and Mr. Dolly increase ???'s tears and can grant Soul Hearts.
- Whore of Babylon is always active.
- Birthright will double the effectiveness of HP upgrades, meaning ??? gains twice as many soul hearts as normal.
- This can be exploited with Converter to generate unlimited HP.
- This can be exploited with
- Fortune Cookie can give a soul heart upon use.
- IBS spawns different kinds of poop, all of which spawn blue flies when ??? destroys them.
- Judas' Tongue lowers the price of Soul Heart Devil deals.
The 
Negative[ | ]
- Items that directly add Red Hearts to the health bar, such as Yum Heart, Yuck Heart or full health pills, are useless. However Eternal Hearts still act as an extra half a heart and become a full soul heart at the end of the floor making Prayer Card viable.
- Blood Donation Machines and Devil Beggars are riskier, as they deplete health that is harder to replenish.
- Cursed Skull will automatically teleport ??? out of the room upon taking any damage, as he doesn't have any Red Hearts. This can be used to easily warp out of the Boss Rush room, but is mostly an annoyance.
- Works only at half a soul heart.
- Glass Cannon will bring ??? down to half a Soul Heart, and not give back any health upon leaving a room due to ???'s lack of Red Hearts. This item essentially takes away most of the player's health in exchange for a single high damage tear.
- This effect no longer applies in Repentance, making it a more viable choice. Even so, caution should be used, as taking damage will cause the next damage taken in the room to be two full soul hearts, making this especially risky for ???.
- Guppy's Paw, since requiring Red Hearts to convert, would be a useless item to hold (but should still be picked up and swapped back to get credit towards the Guppy transformation).
- Guppy's Paw may still be used to activate Broken Remote.
- Little C.H.A.D. is useless unless paired with Dark Bum or Apple of Sodom, where it becomes very useful.
Unlockable Achievements[ | ]
Trivia[ | ]
- ??? appears in the original Binding of Isaac.
- ???'s unlock requirements in Rebirth are the same in the original Binding of Isaac.
- The name "Blue Baby" had not appeared in the game itself until the Afterbirth expansion, with a co-op baby named as such.
- Before Afterbirth, in the original Binding of Isaac, his true name would appear in Isaac's Last Will in parentheses. This detail was overlooked/removed in Rebirth.
- ???'s common nickname, Blue Baby, is a reference to blue baby syndrome, in which a baby's skin complexion appears blue from a lack of oxygen in its blood due to a congenital heart defect.
- Many of Edmund's older flash games from Newgrounds feature ??? and Brother Bobby. ??? was Edmund's mascot from 1996-2002.
- In several cutscenes, Isaac is depicted suffocating inside a chest. ??? is first seen inside an identical chest, and ??? is the follow up boss after Isaac. Blue skin tone is typically used to show suffocation, and X eyes imply that the character is either knocked out or deceased.
- After death, the bowels of the deceased will loosen, causing them to defecate themselves. This is most likely the reason ??? starts with The Poop.
- After death, the bowels of the deceased will loosen, causing them to defecate themselves. This is most likely the reason ??? starts with
- Unlike many of the other characters, ??? does not appear in the Bible or any religious scripture. He is the first character with this distinction, and the only one to appear in the original Binding of Isaac - the second being The Lost in Rebirth, third being Keeper in Afterbirth and fourth being The Forgotten in Afterbirth+.
- The Ankh will resurrect any character as ???, even before he is unlocked.
- Although "Blue Baby" is considered an unofficial nickname for ???, the character is referred to by this name in some of the game's code. One example of this is the image file for the character, named
character_006_bluebaby. - ???'s look originally came from Dead Baby Dressup!, one of Edmund McMillen's first Flash games.
- ???'s starting health is listed as "-I" on the character selection screen.
- As a secret character, ??? does not appear on the character select screen until unlocked.
- He shares this trait with The Lost, Keeper, and The Forgotten.
- He shares this trait with
Gallery[ | ]
??? in ending 10.
Isaac briefly appears as ??? during the cutscene preceding The Beast.
???'s transition screen portrait.
 ??? (Character) Unlocks
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 Mom's Heart Unlocks
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 Characters
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 The Binding of Isaac: Rebirth
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