| Base Health||None|
| Base Damage||3.5|
| Base Fire Rate||1|
| Base Range||23.75|
| Base Speed||1|
| Base Shot Speed||1|
| Base Luck||0|
The Lost is a secret playable character in The Binding of Isaac: Rebirth.
The Lost can only take damage once. Upon receiving damage, The Lost will die. This aspect of The Lost renders many items entirely useless. The Lost may not pick up Red Hearts and any Soul Hearts, Black Hearts, and Eternal Hearts will be discarded upon obtaining them. The Lost does not start with any Collectibles, Consumables, or Trinkets, but rather with 1 Coin. The Lost starts with Flight.
- Curse Rooms should be avoided when playing as The Lost unless the player has a way of exiting the Curse Room without taking damage.
- Items that rely on taking damage should be re-rolled, for they are essentially useless while playing as The Lost.
- The Lost can receive Devil Room Items for free.
- The player should observe rooms for a short while before moving, for some rooms, such as the room full of AIDS Poop on The Chest floor, contain hazards that, if The Lost kept moving, the player would lose the run.
- Dead Cat and 1UP! still work properly, giving you an extra life, and an extra chance should you get hit. It doesn't show up on the HUD though because of a permanent curse of the unknown-like effect.
- Because The Lost has no Health, Whore of Babylon is always active
Unlocking The Lost
The way to unlock The Lost is unique compared to that of the other unlockable characters. The player must perform the following acts both in order and in one game session.
- The player must be killed by a Mulliboom on either The Basement or The Cellar floor as Isaac.
- The player must be killed by one of their own bombs on either The Caves or The Catacombs floor as Magdalene.
- Obtaining Pyromaniac will make this impossible.
- The player must be killed by Mom during the Mom boss fight on either The Depths or the Necropolis floor as Judas.
- This must be from Mom herself, not from any of the Monsters she spawns.
- The player must be killed by Satan during the Satan fight on the Sheol floor as Azazel.
- This must be from Satan himself, not from The Fallen or a Kamikaze Leech.
The player is allowed to restart runs, but only by holding the "R" key. The player can even restart after Isaac has died if they either pause the game and restart or have fast enough reflexes. This must be performed before Isaac's Last Will has appeared on-screen.
- The Lost appears to be Isaac's spirit or soul, as it is depicted floating off-screen from Isaac's corpse upon the death of Isaac.
- Another reason that The Lost seems to be a spirit is that The Lost looks almost identical to Posthumous Suture, Posthumous Suture being a ghost.
- If The Lost is killed and owns Lazarus' Rags, it will respawn as Lazarus II. Achievements for The Lost cannot be unlocked as Lazarus II.
- A similar circumstance occurs when The Lost is killed while owning Judas' Shadow.
- In a post, Edmund has stated that, in the expansion Afterbirth, The Lost will start with spectral tears and the D4.