The Lamb is the boss of the 
Dark Room, and the final boss of Ending 15.
Contents
Behavior[]
Phase 1[]
The Lamb floats towards Isaac and performs the following attacks:
- Fires 2-4 lines of homing projectiles in a spread that rotate to follow Isaac's movements.
- Unleashes a burst of many small
Ipecac-like projectiles in random directions. - Fires 6 rings of 10 projectiles outwards with one projectile always aimed in Isaac's direction. The Lamb continues to move towards Isaac but at a very slow pace while performing this attack.
- Shoots rotating waves of 3 projectiles in a around itself in all directions that split apart once they make contact with any surface, similar to The Parasite.
- Fires 5 rotating lines of projectiles.
- The Lamb occasionally spawns 0-3 Attack Flies during any of the 4 attacks above.
Phase 2[]
Once The Lamb reaches 50% HP, its body detaches from its head and falls to the ground. This phase has each part of The Lamb attacking independently of each other.
The head of The Lamb continues to chase Isaac and can still perform most of the attacks from Phase 1. It loses the explosive shot attack and no longer spawns Attack Flies but gains 3 additional attacks:
- Charges extremely quickly directly towards Isaac, stopping at the edge of the room.
- Stops in place and fires four Brimstone beams in the cardinal directions. The beams can rotate 90 degrees either clockwise or counterclockwise.
- Fires a large burst of homing projectiles towards Isaac, similar to the combination of Monstro's Lung and Spoon Bender.
- Defeating the body first has no effect on the head's behavior.
The body of the Lamb remains stationary at the position the Lamb was at the end of Phase 1. The body has one attack which it performs at random intervals but while the head is attacking:
- Fires a large burst of disorganized projectiles in all directions and spawns up to 5 Attack Flies.
- If the head is defeated first, the body can spawn up to 25 Attack Flies.
- When the body is killed, a Curse of Darkness effect is applied for a long period of time.
Gallery[]
The Lamb in-game.
The Lamb in its second phase.
The Lamb as one of Delirium's forms.
Unlockable Achievements[]
Defeat 
- Ultra Hard - Defeat ??? or The Lamb. Possession of The Polaroid/ The Negative is required, barring getting to Dark Room through a Sacrifice Room. Defeat Mega Satan.
- The gate is open! - Defeat The Lamb.
- Golden God! - Defeat ??? and The Lamb.
- ZIP! - Defeat The Lamb in under 20 minutes.
- It's the Key - Defeat The Lamb without taking hearts, coins, and bombs through an entire run.
- Missing Poster - Defeat The Lamb as Isaac.
- Maggy's Faith - Defeat The Lamb as Magdalene.
- Curved Horn - Defeat The Lamb as Judas.
- ???'s Soul - Defeat The Lamb as ???.
- Black Lipstick - Defeat The Lamb as Eve.
- Samson's Lock - Defeat The Lamb as Samson.
- Demon Baby - Defeat The Lamb as Azazel.
- Pandora's Box - Defeat The Lamb as Lazarus.
- Mystery Sack - Defeat The Lamb as Eden.
- Godhead - Earn all 5 / 9 (except the cent sign for Ultra Greed) / 10 / 12 completion marks on Hard mode as The Lost.
5 / 
9 (except the cent sign for 
10 / 
Notes[]
- The Lamb can be reached before The Negative is unlocked by taking the trapdoor in a Black Market from Sheol if one shows up.
- The Lamb can be reached before The Negative is unlocked if a Sacrifice Room is used 12 or more times.
Trivia[]
- Despite Jesus Christ often being referred to as the "Lamb of God" in the Bible in the books of John and Revelation, The Lamb in this scenario most likely refers instead to the lamb that was sacrificed in Isaac's place in the story of Abraham and Isaac which this game is based upon.
- The music that plays during this battle is titled The Fallen Angel.[1]
- The Lamb is likely a reference to the name of the original Binding of Isaac's DLC expansion, "the Wrath of the Lamb". Due to the absence of any mention of a Lamb in the original game, this may be the character eponymous with The Wrath of the Lamb expansion pack.
- The Lamb's battle portrait depicts it with dark grey bones, but in-game the Lamb has white bones.
- The Lamb shares its name with a level from Edmund's previous game Super Meat Boy.
- The Lamb is one of the three bosses that can dim the room (making a temporary Curse of Darkness effect). The other bosses are Dark One and The Adversary.
- During an AMA stream, Edmund McMillen confirmed that The Lamb is "Isaac, dead, as a demon," and that it represents "his evil side." [2]
References[]
Bugs[]
 Bug!
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If The Lamb is shooting projectiles and you damage it over half of its health, it will continue to fire until dead or it has finished its attack. |
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| Bug!
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Killing the body in around 5 seconds will make the body stand inside of the chest, making you unable to reach it (and end the game). You can fix this by going in and out of the room. |
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| Bug!
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With the special seed BASEMENT and coming with the last sacrifice room reward, opening The Lamb's chest makes the game crash. |
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 The Lamb Unlocks
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 The Binding of Isaac: Rebirth
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