While it's still possible to generate infinite batteries with this synergy, it is slow to do so since mostly Micro Batteries will spawn. The occasional Lil' Battery or other battery spawn is needed to build up the battery pile.
Error: The given pickup ("Rune of Jera") does not exist. can not be duplicated.
Mimic Chests will not be duplicated until their spikes are exposed.
Opened chests will be duplicated into an unopened copy.
A normal Chest may be duplicated into a Red Chest or a Mimic Chest.
A duplicated trinket is mostly useless, as you cannot pick up two of the same trinket even with Mom's Purse, Belly Button, or Smelter.
However, with "consumable" trinkets such as Store Credit or Bag Lunch, it can be extremely powerful.
In combination with a 48 Hour Energy pill and Paper Clip, the initial Locked Chests on Chest can be infinitely duplicated and opened.
In Greed Mode, if a Lil' Battery appears in the Shop and a Error: The given pickup ("2 of Diamonds") does not exist. is acquired, infinite money can be gained by duplicating the Two of Diamonds.
By dropping a card, rune, or pill in a room with no other pickups, then using D1, this item can function similarly to Blank Card and Placebo.
By dropping a card, pill, or trinket in a room with no other pickups, then using D1, this item can function similarly to Deck of Cards, Mom's Bottle of Pills, or Mom's Box (But without the luck up or doubled trinket effects).
A duplicated card has a very rare chance to turn into a Dice Shard, Cracked Key, or Emergency Contact; however, these will always duplicate as themselves instead of duplicating as a card.
A duplicated Gold Pill will turn into a random Pill chosen from the Pill Pool.
When duplicating any type of Chest, the contents of the original Chest will be rerolled. This can be seen with Guppy's Eye.
Synergies[]
Book of Virtues: Spawns one wisp if no pickup is duplicated spawns 2 wisps instead
Tainted Lost: Duplicated cards have an increased chance to be Holy Cards.
In-game Footage[]
Trivia[]
D1 is the only die item that doesn't re-roll anything.
The D1 now creates randomized pickups, meaning that the description is more accurate to the item's effect.
As an exception, Spindown Dice and D10, although they technically do re-roll items/enemies, have a controlled and consistent result.
D1 is the only standard die item that doesn't have the respective number of sides as outcomes, but rather, just a D6 with all sides having singular pips. Rather, an actual D1 would be more accurately pictured as a Mobius strip, a sphere or an actual real-word “denary die” similar in form to a cyllindric object with slanted top and bottom.
Chests, and trinkets.
Dice 
Isaac Unlocks 
Ultra Greedier Unlocks 
The Binding of Isaac: Rebirth
