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|Defeat Satan as IsaacMom's Knife|
- Isaac's tears are replaced by a knife that pierces enemies and can travel through obstacles. Holding down the fire button increases its range and power.
- The knife can hurt enemies while Isaac is holding it.
- The knife deals 2x Isaac's damage while held and 6x damage at the furthest possible point of its arc, regardless of the actual maximum range stat.
- The knife can be held and fired diagonally. Firing the knife diagonally requires a frame perfect input. However, this can be done easily with a controller's analog stick or with Analog Stick+0.3 tears up. Allows Isaac to fire tears diagonally..
- The knife will not work in challenges with the Blindfolded effect.
- 20/20Grants double shot. / Conjoined / The Inner EyeGrants triple shot but decreases tears. / Mutant SpiderGrants quadruple shot but decreases tears.: Isaac holds only one, but shoots multiple knives at their typical spread.
- BrimstoneTears are replaced by a laser beam that pierces through all enemies and obstacles in its path and deals high damage. Can only be fired after a short charge-up period.: Firing the knife also shoots a barrage of knives that goes across the screen, with each knife doing 80% of Isaac's damage. The longer the charge, the more knives are added. This effect does not work with Azazel's default mini brimstone. The brimstone-knives do not benefit from A Lump of CoalThe more distance tears travel, the more damage they will do..
- Chocolate MilkGrants charged tears that deal greater damage when fully charged.: Tears up instead of additional damage or charge effects. Knife will also be colored brown.
- Continuum+2.25 Range Up. +1.5 Tear Height. Isaac's tears travel through walls and appear out of the opposite wall. Isaac's tears also travel over rocks and objects.: The knife can now travel through walls and appear out of the opposite wall but will still have the boomerang effect.
- DiplopiaDuplicates all pickups and item pedestals in the room.: Shoots two knives simultaneously without reducing fire rate.
- Fire MindGrants flaming tears that deal burning damage over time. Tears have a chance to explode on impact with an enemy, which creates a fire at the location of the explosion.: Still applies burning but no longer explodes.
- Flat StoneTears bounce off the floor. Tears that hit an enemy after bouncing deal splash damage to all nearby enemies for 25% of Isaac's tear damage.: Knife bounces as it flies away from Isaac, each bounce splash causing Isaac's base damage.
- The Forgotten: The knife attaches to the Forgotten's bone club, forming a scythe with a larger swing and higher damage.
- Ghost PepperAdds a chance to shoot a fire that damages enemies and remains in place until it deals enough damage or the room is left.: The flames can shoot from Isaac while holding the fire button.
- Gnawed LeafAfter standing still and not shooting for a short time, Isaac turns invincible until he moves or shoots.: The held knife can damage enemies while Isaac is invincible.
- GodheadIncreases damage and range while reducing tears and shot speed. Grants homing tears and tears gain a damaging halo.: The knife homes in on enemies, but it does not gain a damaging halo.
- Guppy Transformation: Knife hits will rarely spawn an attack fly.
- HaemolacriaTears are now fired in an arc. Upon hitting the floor, an obstacle, or an enemy, they burst into many smaller tears in all directions. Increases tear delay.: Haemolacria works at the same time with Mom's Knife, with Haemolacria's fire rate resulting in longer charging.
- Homing Tears: Knives home in on enemies and colors the knife purple. It will stick on enemies for a second and make small lunges towards other enemies.
- IpecacReplaces tears with explosive and poisoning projectiles fired in an arc from the mouth.: Knife turns green, may poison monsters that hit it, and removes Ipecac's damage increase.
- Also adds +4 damage.
- Lost ContactEvery tear has a small shield which will allow it to block one enemy projectile.: The knife will block bullets, even when held.
- The Ludovico TechniqueInstead of firing tears, Isaac controls one floating tear that hover over obstacles. This tear deals constant damage when held in place over an enemy.: Isaac controls a floating knife that deals 2x Isaac's damage. Tears stat is ignored and damage is dealt at a rate equivalent of 5 tear delay.
- The Ludovico Technique + any multi-shot item: Isaac controls a floating knife surrounded by additional rotating knives.
- The Ludovico Technique + Lost Contact: Floating knife loses almost all ability to block bullets, with a tiny area around the hilt that can stop shots.
- The Ludovico Technique + Loki's HornsGives a random chance for projectiles to fire in all 4 cardinal directions.: Loses Loki's Horns effect; Isaac controls only one floating knife.
- Monstro's LungIncreases damage and grants a charged shot that fires multiple tears in the same fashion as Monstro.: Fires a cluster of 3-5 knives at maximum charge, each dealing 2x damage.
- ProptosisTears start out massive with high damage, and then shrink down and become weaker over a short range.: The Knife deals double damage regardless of range.
- Strange AttractorPickups, trinkets, and monsters are magnetically attracted to Isaac's tears.: Enemies are pulled towards the knife. The effect is minor while not firing and much stronger while the knife is launched.
- Tammy's HeadShoots 10 tears in a circle around Isaac, which retain the damage, shot speed, and special effects (such as poison) of Isaac's tears.: Fires 10 knives in a circle around Isaac, dealing massive damage.
- Tech XTears are replaced with laser rings that pierce through enemies and deal damage to enemies within them. Can be charged to increase the size of the ring.: Both fire normally.
- Technology 2Decreases damage and replaces right eye tears with a unlimited range, piercing laser which fires continuously.: While charging Mom's Knife, Technology 2 will still fire.
- Trinity ShieldIsaac gains a shield that protects him from enemy shots.: Blocks bullets in the direction the knife is held, giving enough protection to walk up to and melee enemies, or just to safely shoot the knife.
- Unicorn StumpUpon use, grants invulnerability and increased speed for five seconds, but removes the ability to shoot tears. and other invincibility items: Even though the knife cannot be fired, the knife will deal damage while Isaac is invincible.
- Anti-Gravity-2 Tear Delay. Tears float in position until firing ceases, after which they will fly off in the direction they were shot in.: Only tear delay down applies.
- Apple!Increases tears. Adds a chance to fire a high-damage razor blade. / EuthanasiaAdds a chance to fire needles. If a needle kills an enemy, it bursts into more needles. / Tough LoveAdds a chance to shoot a tooth instead of a tear, which deals greater damage than regular tears.: No chance of higher damage or instant kills.
- Compound FractureIncreases range. Tears turn into bones, which shatter into 1-3 bone shards upon hitting an enemy or obstacle. / Cricket's BodyGrants -1 Tear Delay and reduces Range. When tears hit an object or deplete their range, they spawn 4 smaller tears, whose Range and Damage scale with Isaac's. / The ParasiteIsaac's tears split in two when they hit something.: Only stat effects, if any, apply without splitting.
- Cursed EyeGrants charged tears that can be fired in a tight burst of four. Getting hit while charging will teleport Isaac into another room.: Overridden by Mom's Knife.
- Dr. FetusTears are replaced by bombs that benefit from bomb-enhancing effects and slide for a fixed time after being fired.: Overridden by Mom's Knife.
- Both the knife and the bombs fire normally.
- Epic FetusIsaac's tears are replaced with guided missiles, like those used by the Doctor's Remote.: Overridden by Epic Fetus.
- Each explosion shoots 10 knives in a circle from the point of impact.
- ExplosivoIsaac's tears have a chance to stick to enemies and explode.: Overridden by Mom's Knife.
- Eye of BelialGrants piercing tears. After piercing one enemy, tears start homing and deal double damage.: Overridden by Mom's Knife.
- Holy LightIsaac has a random chance to fire a Holy tear, which, when it hits an enemy, will spawn a Crack the Sky-style light beam on the same enemy, dealing damage.: Overridden by Mom's Knife.
- Holy Light can trigger on both held and thrown knives.
- LachryphagyIsaac's tears decelerate as they travel. Upon stopping or hitting an obstacle, they burst into 8 tears in all directions. Tears can be fired into other tears to feed them, increasing their damage.: Overridden by Mom's Knife.
- Little HornAdds a chance to fire a piercing tear that instantly kills any enemy that it touches.: Overridden by Mom's Knife.
- A Lump of CoalThe more distance tears travel, the more damage they will do.: No effect on the knife regardless of range.
- MarkedIsaac will now fire tears automatically directed at a red target on the ground which is controlled by the player. This allows for a full 360 degree tear firing radius. Can be overridden by other tear modifiers such as Mom's Knife or Brimstone.: Only tears up and range up apply.
- Monstro's LungIncreases damage and grants a charged shot that fires multiple tears in the same fashion as Monstro.: Overridden by Mom's Knife.
- Firing a knife causes several other knives to shoot out at random directions.
- My ReflectionGives Isaac's tears a boomerang effect, and increases range and shot speed.: No effect.
- Mysterious LiquidTears leave a small, short lasting pool of creep on impact or when their range is depleted.: Overridden by Mom's Knife.
- The Knife leaves creep trails while fired.
- Pop!Replaces Isaac's tears with eyeballs that can bounce off of each other. The eyeballs are not limited by range, and will instead dissipate when they stop moving or when hitting an enemy or obstacle.: Overridden by Mom's Knife.
- ProptosisTears start out massive with high damage, and then shrink down and become weaker over a short range.: Damage is doubled and no damage decrease with distance.
- Rubber CementTears bounce off walls, enemies, and environmental objects.: Overridden by Mom's Knife.
- TechnologyReplaces tears with a piercing laser with unlimited range.: Overridden by Mom's Knife.
- Both the knife and the laser fire normally.
- Tiny PlanetRange up and makes shot tears revolve around Isaac until they drop.: Knives go in a spiral around Isaac; the longer the knife is charged, the bigger the spiral. Not recommended, as this makes Mom's Knife almost impossible to aim.
- TrisagionTears are replaced with piercing white blasts of light.: Overridden by Mom's Knife.
- This item is used in Challenge #26 (I RULE!).
- In the original Binding of Isaac, buying the item from the Devil Room cost 1 heart container instead of 2.
- The description of the item is a possible reference to the sniper's dialogue in Team Fortress 2.
6PG9 7RK3 (Treasure room up and to the right one room from spawn)
DVNV YV9Y (Treasure room adjacent to spawn)
JW43 H8EK (Treasure room adjacent to spawn)
1M9E Y1G1 (Treasure room adjacent to spawn)
P8SE A9JW (Treasure room adjacent to spawn)
S63T 434W (Treasure room adjacent to spawn)
Z3SL DS3W (hard; first floor treasure room)
Bug! The Blindfolded condition also applies to the knives fired by Tammy's Head, and prevents it from working.
- Broken ShovelWhile held, causes multiple Mom's Foots to come down and stomp on Isaac. One of two parts necessary to create Mom's Shovel.
- Broken ShovelOne of two parts necessary to create Mom's Shovel.
- Divorce PapersSpawns a Mysterious Paper, increases tears, and grants a bone heart.
- Mom's Bottle of PillsGives Isaac a random pill, and will cause him to drop any held Q-slot item (If any). The player will only receive six different pill types in one playthrough.
- Mom's BoxWhen used, Mom's Box will drop a random trinket on the ground. While held, increases luck by 1 and doubles the effects of trinkets.
- Mom's BraUpon use, petrifies all enemies in the current room for approximately 4 seconds.
- Mom's Coin PurseSpawns 4 random pills around Isaac.
- Mom's ContactsAdds a chance to shoot petrifying tears, which stop enemies in place and prevent them from moving or attacking. Range up.
- Mom's EyeAllows Isaac to fire tears from the back of his head.
- Mom's EyeshadowTears have a chance to charm enemies.
- Mom's HeelsIncreases range.
- Mom's KeySpawns 2 keys. Generates additional pickups from chests.
- Mom's KnifeIsaac's tears are replaced by a knife that pierces enemies, can travel through obstacles, and can hurt enemies while Isaac is holding it. Holding down the fire button before firing increases its range and power.
- Mom's LipstickIncreases range and shot height.
- Mom's PadUpon use, inflicts fear to all enemies in the room for 5 seconds.
- Mom's Pearls+1.25 Range Up. +0.5 Tear Height. +1 Luck Up.
- Mom's PerfumeAdds a chance to shoot fear tears and decreases tear delay by 1.
- Mom's PurseAllows Isaac to hold 1 additional trinket.
- Mom's RazorSpawns an orbiting razor that damages enemies it touches and inflicts bleeding on enemies, causing them to slowly take damage over time.
- Mom's ShovelSpawns a trapdoor that leads to the next floor upon activation. Unlocks The Forgotten when used on a mound of dirt that appears in The Dark Room.
- Mom's UnderwearIncreases range.
- Mom's WigAdds a chance to spawn blue spiders when firing tears. Restores 1 red heart.
- Mom's LocketGrants half a red heart each time a key is used. Converts half red heart pickups into full red hearts.
- Mom's PearlGrants a secondary 10% chance of any non-specific heart drop turning into a soul heart.
- Mom's ToenailMom's foot randomly stomps down somewhere in the room. 1 minute intervals.
|Mom's KnifeDefeat Satan as IsaacThe D20Defeat ??? as IsaacIsaac's HeadComplete the Boss Rush as IsaacIsaac's TearsDefeat Isaac as IsaacMissing PosterDefeat The Lamb as IsaacLost BabyDefeat Mom's Heart on hard mode as Isaac||Fart BabyDefeat Hush as IsaacLil' ChestDefeat Ultra Greed as IsaacCry BabyDefeat Mega Satan as IsaacBuddy BabyEarn all hard mode completion marks as IsaacI RULE!Defeat ??? or The Lamb for the 1st time, and defeat Satan as Isaac||D InfinityDefeat Delirium as IsaacD1Defeat Ultra Greedier as Isaac|
|The Binding of Isaac: Rebirth|
|Achievements||Attributes||Bosses||Cards and Runes||Challenges||Chapters|