??? (Character)

???, 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.

Item Interactions

 * : Soul hearts gained from health ups will be doubled. Health down pills will remove 2 soul hearts instead of 1, however.

Positive

 * 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.
 * will give 2 black hearts on pickup, granting its effects essentially for one heart.
 * is effectively a for ???.
 * can be used to produce black hearts upon taking damage.
 * Balls of Steel pills or grant two soul hearts, both of which are more useful than normal HP up items.
 * The grants one soul heart as well as lifting any curses.
 * The card gives ??? a permanent soul heart.
 * Spawns soul hearts.
 * costs three Soul Hearts and grants three Black Hearts and damage up. Like, this item is always safe to take.
 * will always activate when entering a room, but still deactivates after taking damage.
 * and Daemon's Tail replace useless Red Hearts with Soul and Black Hearts respectively.
 * converts useless Red Hearts into Black Hearts and Spiders.
 * Dark Bum can now also drop pills, cards, and runes, which can include The Hierophant, Balls of Steel, or Dagaz.
 * 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, providing a consistent stat boost.
 * has a chance to spawn Soul Hearts when hit.
 * turns all uses into holy poops.
 * 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.
 * can produce Black Hearts.
 * makes create Golden Poop.
 * Monkey Paw will drop 3 Black Hearts, but must take damage for each one to spawn.
 * Petrified Poop is useful early on to get more pickups from every room.
 * and will always activate when taking damage.
 * , which is generally useful, is especially useful to ??? as it spawns Soul Hearts.
 * generates Black Hearts.
 * Using Satanic Bible now also causes boss items to turn into devil deals that cost hearts, so it may be best to hold off on using it until after the boss fight.
 * 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 ???.
 * and increase ???'s tears and can grant Soul Hearts.
 * is always active.
 * will double the effectiveness of HP upgrades, meaning ??? gains twice as many soul hearts as normal.
 * This can be exploited with to generate unlimited HP.
 * can give a soul heart upon use.

Negative

 * Items that directly add Red Hearts to the health bar, such as, 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.
 * If ??? has only one heart, has a chance to be lethal.
 * 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.
 * 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 all subsequent damage taken in the room to be two full soul hearts, making this especially risky for ???.
 * , 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.
 * Judas' Tongue doesn't lower the price of Soul Heart Devil deals.
 * is useless unless paired with, where it becomes very useful.

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.
 * ???'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 . ??? 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.
 * 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.
 * The 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.
 * ???'s look originally came from Dead Baby Dressup, one of Edmund McMillen's first Flash games.
 * ???'s starting health is listed as "-1" on the character selection screen.