Upon use, Isaac holds an Eraser above his head, which can be thrown in any cardinal direction. Upon hitting a monster, the enemy will be "erased", preventing any of the same enemy from appearing for the rest of the run.
Deals 15 damage to bosses. If fatal, erases the boss for the rest of the run.
Can only be recharged by entering a new floor. Batteries and most other methods of recharging have no effect.
Notes
Erased enemies and bosses appear as a brief pink puff of smoke. Any on-death effects are not checked.
The Seven Deadly Sins minibosses and Angels will still drop their respective pickups or items.
If used on multistage bosses like Hush or Ultra Greed, erasing the first phase skips any further phases.
If Eraser's projectile hits an enemy's projectile that has collision with Isaac's tears and isn't considered an enemy (e.g. Fire Worm's fire, Coal Boy's coal, Big Bony's thrown bone) it has no effect and Eraser's projectile will be destroyed .
Although the thrown Eraser cannot hit friendly enemies these enemies can still be erased if their hostile variants are erased. This also means that when effects such as Friend Finder attempts to spawn an erased enemy it only creates the brief puff of pink smoke wasting the effect.
Erased enemies will remain erased if a Victory Lap is started.
Erased enemies will also remain erased if items such as R Key or Genesis are used.
It is possible to erase Chubber's launched Charger, rendering it unable to attack.
Erasing Poltys will render Haunted Chests harmless, but may make some rooms impossible to complete without bombs or flight as they rely on a Polty clearing a path.
Each floor traveled up during the Ascent will recharge the Eraser.
If a segmented worm-boss such as Larry Jr. or Scolex is removed via Eraser, Delirium will disappear if it attempts to turn into that boss. This will spawn the ending chest and count as having defeated Delirium. Other multipart bosses' erased pieces may be unable to spawn, but do not kill Delirium entirely.
Erased enemies don't grant exploration bonuses in Daily Challenges.
Angelic Prism: Throwing the Eraser through the Angelic Prism will cause it to split into four.
The Battery: The eraser can gain an extra charge if it is not used on one floor.
Bethany / Tainted Bethany: Soul and blood charges can be used with the Eraser, allowing multiple uses per floor.
Blood Puppy: Throwing the Eraser at an enraged Blood Puppy (second stage) will 'erase' its enraged form, keeping it permanently tame.
Throwing the Eraser at its third stage will make it cycle through its normal and second stage as it kills enemies.
Book of Virtues: Spawns a pink eraser wisp on the middle ring. The wisp is immune to projectiles. If a non-boss enemy touches the wisp, it is erased and the wisp is destroyed. The wisp cannot erase bosses, regardless of how much health they have left.
Void: An eraser can be thrown with each use of Void after absorbing it, allowing multiple uses per floor.
Tainted Lazarus: Enemies erased in one form will still be erased when Tainted Lazarus flips.
Interactions
9 Volt / Battery Pack: Item doesn't fully charge the Eraser when picked up.
My Shadow / Shade: Erasing a Charger will prevent all newly created friendly Chargers from spawning, rendering the item useless as this item spawns a normal Charger before changing it to the special My Shadow variant.
Sharp Plug: Attempting to recharge the Eraser with the Sharp Plug hurts Isaac for half a heart without recharging the item.
Habit: Taking damage with Habit will not charge Eraser.
Eraser originates from the Antibirth mod. In Antibirth, this item was single use and wouldn't permanently remove an erased boss from the run, but could kill any boss in one hit.
The Pickup quote was "Erase your enemies!".
This item's effect is similar to the scroll of genocide that appears in traditional roguelikes such as NetHack, originating in the Hack variant Hack121.
Bugs
Bug!
If used to kill Dogma or the Mom's Heart leading to Corpse, it will not count it as a kill, preventing progress on the respective paths.
Hush or 
Ultra Greed, erasing the first phase skips any further phases.
Stone Grimaces, lowered 
Hosts, or 
Eternal Flys.
Bulbs can steal charges from the Eraser.
Fire Worm's fire, 
Coal Boy's coal, 
Big Bony's thrown bone) it has no effect and Eraser's projectile will be destroyed .
Friend Finder attempts to spawn an erased enemy it only creates the brief puff of pink smoke wasting the effect.
Ultra Greed Coins or 
Little Horn's 
Dark Balls are considered enemies and can be erased.
Chubber's launched Charger, rendering it unable to attack.
Poltys will render 
Haunted Chests harmless, but may make some rooms impossible to complete without bombs or flight as they rely on a Polty clearing a path.
Larry Jr. or 
Scolex is removed via Eraser, 
Delirium will disappear if it attempts to turn into that boss. This will spawn the ending chest and count as having defeated Delirium. Other multipart bosses' erased pieces may be unable to spawn, but do not kill Delirium entirely.
? Card: Can throw an additional Eraser.
Angelic Prism: Throwing the Eraser through the Angelic Prism will cause it to split into four.
The Battery: The eraser can gain an extra charge if it is not used on one floor.
Bethany / 
Tainted Bethany: Soul and blood charges can be used with the Eraser, allowing multiple uses per floor.
Blood Puppy: Throwing the Eraser at an enraged Blood Puppy (second stage) will 'erase' its enraged form, keeping it permanently tame.
Book of Virtues: Spawns a pink eraser wisp on the middle ring. The wisp is immune to projectiles. If a non-boss enemy touches the wisp, it is erased and the wisp is destroyed. The wisp cannot erase bosses, regardless of how much health they have left.
Void: An eraser can be thrown with each use of Void after absorbing it, allowing multiple uses per floor.
Tainted Lazarus: Enemies erased in one form will still be erased when Tainted Lazarus flips.
9 Volt / 
Battery Pack: Item doesn't fully charge the Eraser when picked up.
Car Battery: No effect.
Kidney Stone / 
Number One / 
Pluto / 
Inner Child's revive: Lowers the Eraser's range drastically and can only be improved with tear height ups.
My Shadow / 
Shade: Erasing a 
Charger will prevent all newly created friendly Chargers from spawning, rendering the item useless as this item spawns a normal Charger before changing it to the special My Shadow variant.
Sharp Plug: Attempting to recharge the Eraser with the Sharp Plug hurts Isaac for half a heart without recharging the item.
Habit: Taking damage with Habit will not charge Eraser.
Bug!
Dogma or the 
Mom's Heart leading to 
Corpse, it will not count it as a kill, preventing progress on the respective paths.
The Binding of Isaac: Rebirth
