Missing No. 
Effects
- Randomizes passive items and attributes on pickup and at the start of every floor.
- Stats gain a random flat modifier. These modifiers do not stack between levels and are instead rerolled every time.
- Speed -0.2, 0 or +0.2.
- (Removed in Repentance) Also affects maximum speed, may never exceed 2.0.
- Range -1.5, 0 or +1.5.
- Tears -0.5, 0 or +0.5.
- Shot speed -0.2, 0 or +0.2.
- Damage -1, 0 or +1.
- Luck -1, 0 or +1.
- Does not affect trinkets, cards, pills, Pretty Flies,
The Polaroid / 
The Negative, 
Key Piece 1 / 
Key Piece 2, (Added in Repentance)
Knife Piece 1 / 
Knife Piece 2, or active items.
Notes
- See
D4 for more details of the rerolling process.
- Like other full-reroll effects, Missing No. has a small chance to not reroll every item.
- (Removed in Repentance)Can cause transformations.
- (Added in Repentance) Transformations are lost when rerolling out of the items that caused them.
- Missing No. cannot be re-rolled or removed by most means after being picked up, including D4, (Added in Repentance)
Genesis, (Added in Repentance)(XVII - The Stars?) XVII - The Stars?, or taking damage as (Tainted Eden) Tainted Eden.
Synergies
- (Added in Afterbirth †)(Butter!) Butter!: Provides the only available method for getting rid of Missing No.