Isaac'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.
"Stab stab stab"
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.
This item belongs to the Yes Mother? set. Collecting three items from this set will transform Isaac into his mother.
20/20 - Isaac holds only one, but shoots multiple knives at their typical spread.
The Inner Eye - Isaac holds only one, but shoots multiple knives at their typical spread.
Mutant Spider - Isaac holds only one, but shoots multiple knives at their typical spread.
Brimstone - 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
The Ludovico Technique - Isaac controls a floating knife that does 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 Horns: Loses Loki's Horns effect; Isaac controls only one floating knife.
The Ludovico Technique +
Brimstone: Mom's Knife overrides Brimstone leaving only the floating knife.
Monstro's Lung - Fires a cluster of 3-5 knives at maximum charge, each dealing 2x damage.
Proptosis - The Knife deals double damage regardless of range.
Strange Attractor - Enemies are pulled towards the knife. The effect is minor while not firing and much stronger while the knife is launched.
Tammy's Head - Fires 10 knives in a circle around Isaac, dealing massive damage.
Tech X - Both fire normally.
Overridden by Mom's Knife.
Unicorn Stump - Even though the knife cannot be fired, the knife will deal damage while Isaac is invincible.