Mother

This article is about the final boss of Corpse. For the boss of chapter 3 and chapter 3.5, see Mom.
**Mother** is a boss added in *The Binding of Isaac: Repentance* and the only boss of the second floor of the Corpse, as well as the final boss of Ending 21.

## Behavior

Upon entering the boss room in Corpse II, the room is empty except for a hole in its center. Walking into it drops Isaac down into the arena where Mother is fought.

### Phase 1

Mother begins the fight attached to the top of the room and is stationary, similar to Mega Satan. Her face and hands can all be attacked to deal damage to her, and she uses them separately in her attacks:

* One of Mother's hands grabs a knife and throws it directly downwards. The knife emits projectiles horizontally while travelling and a burst of many projectile lines in a radius upon impacting the back wall.
* One of Mother's arms releases trails of projectiles that move across the arena in a wave pattern, eventually homing in on Isaac.
* One of Mother's hands slams the ground, releasing streams of projectiles in a radius and spawning Small Maggots.
	+ Small Maggots that land on top of Mother's hitbox do not spawn.
* Occasionally, Mother spits out a unique Fistula at Isaac that bounces off walls. Mother swipes the Fistula towards Isaac whenever it travels close to one of her hands and releases 2 lines of 8 projectiles when it collides with the bottom wall. Mother repeats this several times, causing the Fistula to gradually gain speed, before slamming a hand down on the mass, crushing it and sending 3 medium Fistulas outwards. Each medium Fistula flies until it collides with a wall, sending out 2-3 small Fistulas and being destroyed in the process. These small Fistulas travel a short distance before bursting and spawning a Small Maggot.
	+ This Fistula can be reflected back towards Mother through the use of a variety of melee-based attacks, each reflect causing the Fistula to glow brighter. Successfully reflecting the Fistula 6 times will cause it to be destroyed upon contact with Mother, dealing damage to and briefly stunning her. It will also burst into 8 medium Fistulas in a radius that disappear quickly, six of which deal damage to Mother; each of these can also deal damage to Isaac. Abilities that can cause this interaction include:
		- 's spin attack.
		- The Forgotten/'s bone swing.
		- Tainted Samson//'s donkey jawbone swing.
		- 's swipe.
		- Tainted Magdalene's hug attack, though it cannot be triggered by the Fistula.
* Occasionally, Mother retreats upwards, becoming invulnerable, and summons a horde of 34 Dead Isaacs at the bottom of the arena that walk up towards Mother. If any are left alive to reach Mother, she swipes with a hand, killing any that are caught in the swipe, releasing a tiny burst of red projectiles, and launching their corpses towards Isaac. After a while, she ends this attack by slamming down both hands, which causes a small rock wave to appear beneath any remaining Dead Isaacs, killing them, and launching their corpses up into the air.

### Phase 2

After losing 2222 HP, Mother retracts her head and arms into her body before releasing a green  laser down the middle of the arena, destroying the lower wall and expanding the area of the room. She then separates from the top wall, launching her head into the center of the room. From this point on, she slides slowly towards Isaac when she isn't performing one of her attacks:

* Spins around in place, shooting out strings of wavy projectiles in all directions.
* Inhales and draws Isaac to her as projectiles appear behind Isaac as he moves. After that, she shoots a massive ball of projectiles towards Isaac that splits into many smaller clusters when hitting a wall, which each then send out lines of projectiles when they collide with a wall or Mother.
* Leaps upwards off-screen before charging vertically across the half of the room which Isaac is located within, then across the other half in the opposite direction. The half she charges across first is telegraphed by a splat at the top or bottom of the room. After this, she slams down in the middle of the room, sending rock waves and small strings of projectiles in all directions.
* Faint white lines appear at set intervals along a random arena wall before a line of projectiles quickly shoots out of the wall along each line; these projectiles hover for a moment before dropping. One line of projectiles is always lined up with Isaac's position. This attack is repeated five times.

## Gallery

* Mother in-game.
* Mother in her second phase.
* Fistula's appearance in Mother's attack.
* Mother's full splash art.
* Mother's old splash art in *Antibirth* from when she was called "The Witness".
* Concept art of an older version of Mother back when she was called "The Witness" for Antibirth. Notably, it has a scrapped 2nd phase that neither made it in the *Antibirth* mod nor the *Repentance* DLC.
* Later concept art of Mother (earlier known as "The Witness") transitioning from phase 1 to phase 2. This transition was adapted into both the *Antibirth* mod and the *Repentance* DLC.
* Boss screen mockup of the "Ur-Gurdy" a design which would later be adapted for "The Witness" and Mother.
* In-game mockup of "Ur-Gurdy's" fight.

## Unlockable Achievements

* A Strange Door - Defeat **Mother**.

* Jacob and Esau - Defeat **Mother**.

* Seeing Double - Defeat **Mother**.

* Isaac's Awakening - Defeat **Mother**.

* Meat Cleaver - Defeat **Mother** as  Isaac.

* Yuck Heart - Defeat **Mother** as  Magdalene.

* Guppy's Eye - Defeat **Mother** as  Cain.

* Akeldama - Defeat **Mother** as  Judas.

* Eternal D6 - Defeat **Mother** as  ???.

* Bird Cage - Defeat **Mother** as  Eve.

* Bloody Gust - Defeat **Mother** as  Samson.

* Devil's Crown - Defeat **Mother** as  Azazel.

* Tinytoma - Defeat **Mother** as  Lazarus.

* 'M - Defeat **Mother** as  Eden.

* Lost Soul - Defeat **Mother** as  The Lost.

* Blood Puppy - Defeat **Mother** as  Lilith.

* Keeper's Sack - Defeat **Mother** as  Keeper.

* Lil Portal - Defeat **Mother** as  Apollyon.

* Bone Spurs - Defeat **Mother** as  The Forgotten.

* Revelation - Defeat **Mother** as  Bethany.

* Magic Skin - Defeat **Mother** as  Jacob and Esau.

* Dice Bag - Defeat **Mother** as  Tainted Isaac.

* Mother's Kiss - Defeat **Mother** as  Tainted Magdalene.

* Lucky Sack - Defeat **Mother** as  Tainted Cain.

* Number Magnet - Defeat **Mother** as  Tainted Judas.

* Ring Cap - Defeat **Mother** as  Tainted ???.

* Lil Clot - Defeat **Mother** as  Tainted Eve.

* Swallowed M80 - Defeat **Mother** as  Tainted Samson.

* Azazel's Stump - Defeat **Mother** as  Tainted Azazel.

* Torn Card - Defeat **Mother** as  Tainted Lazarus.

* Modeling Clay - Defeat **Mother** as  Tainted Eden.

* Crystal Key - Defeat **Mother** as  Tainted Lost.

* Adoption Papers - Defeat **Mother** as  Tainted Lilith.

* Cursed Penny - Defeat **Mother** as  Tainted Keeper.

* Apollyon's Best Friend - Defeat **Mother** as  Tainted Apollyon.

* Hollow Heart - Defeat **Mother** as  Tainted Forgotten.

* Beth's Essence - Defeat **Mother** as  Tainted Bethany.

* Found Soul - Defeat **Mother** as  Tainted Jacob.

* Godhead - Earn all  5 /  9 (except Ultra Greed) /  10 /  12 Completion Marks on Hard mode as  The Lost.

## Damage Scaling

Damage scaling is an unclear mechanic introduced by Nicalis in The Binding of Isaac: Afterbirth to provide a more challenging experience to the players, enabling *some* enemies to retaliate against high damage attacks by deploying an "armor" of a sort to greatly reduce the amount of damage taken. Further details and an in-depth explanation may be found here.

## Strategies

* works on Mother, but only kills one of her phases. If you are holding a Chaos Card, it is recommended to use it in Phase 2, since Mother's attacks are much more dangerous.
* can be very useful, since Troll Bombs will attempt to spawn near Mother, and bombs in *Repentance* will deal 100 damage and ignore the armor. Around 43 bombs would be able to kill her, which corresponds to about 6~7 times of damage. This will be affordable if you have more than 10 hearts in total.
	+ Similarly, using , , or your own Bombs will also help.
* Her charging attack in Phase 2 can be greatly stalled by placing a bomb in front of her path, while also dealing damage to her in the process.
* In phase 2, if the player has , they can bring Mother to a complete standstill while she's charging if they enter statue form in front of her.
	+ Pair this with at least one offensive familiar and the fight becomes a joke for all characters.
* Using  during the Dead Isaac attack will spawn 10 hearts on average, which should keep any red heart characters alive for quite some time. Using it during the hand slam attack that spawns Small Maggots will usually spawn 3-5.
* Using  on Mother's first phase allows phase 2 to be skipped as long she has 15 health or less.

## Notes

* Using  *will* kill Mother in time if you have an extra life. Even though Isaac dies well before the animation is complete, the game over screen will pop up almost immediately after the animation ends. If Isaac has an extra life item that revives him outside the room, he will be able to enter the Final Boss Chest without fighting Mother again.
	+ Killing Mother in this way will *not* reward the completion mark for the current character if they don't have an extra life.
* or any items that inflict Charm can cause Mother's wavy projectiles during the first phase and second phase to target herself.
* The ball of splitting projectiles in Mother's second phase can also collide with Mother. The player can therefore move to the opposite side of Mother after she fires to more easily dodge the attack.
* Unlike most other bosses, Mother has no visible health bar in either of her phases, so it is impossible to tell how much damage you are dealing to her without .
* works on Mother, but in Mother's first phase, Isaac can pick up only one of her parts at a time, either her head or one of her arms, and give it a suplex.
* will damage Mother even though it can be considered another form of Mom.
* Using  will not stop Mother's wavy projectiles from proceeding once the black hole has diminished, causing an un-dodgeable attack. Using this item during the fight is highly ill-advised.

## Trivia

* The Ending following this fight reveals Mother to be a grotesque, undead representation of Mom imagined by Isaac before the events of the game.
* This boss originates from the *Antibirth* mod, and was originally named "The Witness".
	+ The Witness itself was first designed as a boss mockup by the name of "Ur-Gurdy", tying it into the Mama Gurdy line and explaining its visual similarities to that line.
* Between her original appearance in *Antibirth* and *Repentance*, Mother’s boss fight was changed drastically, including the arena being shrunken dramatically, the replacement of several attacks with new ones, the boss theme being changed, and the boss's death animation being changed, along with the addition of Mom’s voice lines during the battle.
	+ Because of how she died in *Antibirth* (turning to stone), it was possible to softlock the game by killing The Witness where the ending chest spawned.
	+ In *Antibirth*, the Corpse II boss room contained four golden chests with items (similar to the starting room in Chest). In *Repentance*, the boss room is completely empty except for the hole leading to the fight against Mother.
* Mother's boss theme is called "Morticide". "Morti-" stems from Latin "Mors" which means "death" or "corpse", while "-cide" means "an act of killing", so the track name effectively means "Killing the dead".
* The back wall of the fight is actually part of Mother's model; attempting to summon her via the console will change the wall of the current floor to a Corpse wall.
* Unlike Mom, Mom's Heart, and It Lives, Mother is not instantly killed by using .
* Mother is one of the only three bosses that don't have a visible health bar of their own. The others are Mega Satan and The Beast.
* Faint translucent Chubber projectiles can be seen leading the lines of projectiles in Mother's second phase white line attack.
* In *Antibirth*, The Witness was immune to Status Effects.
* The reaction of  to the Fistula attack is likely a reference to the "Dead Man's Volley" commonly seen during boss fights in *The Legend of Zelda*.
* The mega brimstone laser when starting phase 2 is a reference to Nuclear Throne's boss, the Nuclear Throne.
* Mother beating up Dead Isaacs in one of her attacks could be alluding to how Isaac gets beaten up in life after leaving his room.
* Mother spawning 34 Dead Isaacs might be a reference to there being 34 characters.