D1

Effect[]

Duplicates 1 random pickup in the current room, including cards, runes, chests, and trinkets.

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, Placebo, and Clear Rune.
Rune of Jera can not be duplicated.
Mimic Chests will not be duplicated.
A normal Chest may be duplicated into a Red Chest or a Mimic Chest.
Opened chests will be duplicated into an unopened copy.
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.
It is possible to duplicate Shop pickups that have not been purchased yet.
With Car Battery, it is possible to infinitely generate Lil' Batteries from a single Lil' Battery.
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 2 of Diamonds is acquired, infinite money can be gained by duplicating the Two of Diamonds.
With a ? Card and Schoolbag, single use items can be used an unlimited number of times by duplicating the card.

Book of Virtues: Spawns two white six-sided die wisps, on the middle ring, at the same time. An extra wisp spawns if no pickups are duplicated.

D1 is the only die item that doesn't re-roll anything.
- As such, its description, in certain cases, can be ironic, as the outcome is entirely predictable if there's only one pickup. This makes sense because the die only has one pip on each of its 6 sides.
- As an exception, Spindown Dice, although it technically does re-roll items, has 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 or a sphere.