Upon use, replaces all monsters in the room with weaker monsters. Each monster type has a specific weaker monster it will transform into. If the monster is already at its weakest level, it usually transforms it into a background critter or kills it outright.
Some enemies can be transformed into obstacles or pickups instead.
Re-rolling a monster will replace it with an entirely new one from any floor, making it dangerous to use early on in the game (as Isaac could get monsters from Depths or later).
The D10 will not reroll Bosses but can reroll monsters spawned by bosses.
Using this item can cause some rooms to become impossible to clear. Jumping or flying monsters may become trapped behind rocks after being rerolled, and therefore become unbeatable.
Sealed doors open after 2 minutes, though there are situations that can prevent this failsafe from triggering.
Flying monsters will only be rerolled into other flying monsters, and ground monsters can only be rerolled into ground monsters. ( Horfs are classified as ground monsters by the D10).
Some invincible enemies will be rerolled, while others (including most Grimace variants) are completely unaffected.
Using this item in a room with Mom's Hand can be very dangerous, as unless they have already landed, they will be directly on top of Isaac, resulting in the new monsters spawning directly on top of Isaac, instantly dealing contact damage.
Using this item, then exiting the room, such as by teleporting or a bombed door, will cause the enemies to be in their original forms upon Isaac's return.
Synergies
Book of Virtues: Spawns orange wisps in the middle ring. Tears shot from these wisps have a 10% chance to replace enemies with their weaker variants.
D10 was voted the worst quality 0 item in the game in a poll on the Binding of Isaac subreddit, resulting in its consequent rework and upgrade to quality 1.
Bugs
Bug!
The D10 can reroll the Suture half of Blighted Ovum.
Bug!
Using this item on any monster with several pieces will reroll every piece into a monster. Mr. Maw and Gemini's cord dots are considered pieces, each turning into a new monster.
Bug!
Rarely, a monster can be rerolled into the mask half of the Mask + Heart enemy, and the mask will die instantly.
Bug!
The Attack Fly, Swarm, and Camillo Jr. enemy can't be rerolled (even though monsters can be rerolled into them).
Bug!
Using this item in a room with Stone Grimaces will turn them invisible. They will not fire, but the space they occupied will prevent Isaac from moving through it like an invisible wall.
Bug!
D10 and items related to it can reroll frozen enemies into alive ones, effectively bringing them back to life.
Upon use, re-rolls all monsters in the room.
Upon use, replaces all monsters in the room with weaker monsters. Each monster type has a specific weaker monster it will transform into. If the monster is already at its weakest level, it usually transforms it into a background critter or kills it outright.
Depths or later).
Flying monsters will only be rerolled into other flying monsters, and ground monsters can only be rerolled into ground monsters. ( 
Horfs are classified as ground monsters by the D10).
Mom's Hand can be very dangerous, as unless they have already landed, they will be directly on top of Isaac, resulting in the new monsters spawning directly on top of Isaac, instantly dealing contact damage.
Book of Virtues: Spawns orange wisps in the middle ring. Tears shot from these wisps have a 10% chance to replace enemies with their weaker variants.
Car Battery: Weakens affected enemies twice.
Broken Remote: Using D10 while holding this will first teleport Isaac, and then reroll the enemies in the new room.
This trait is shared with 
D7 and 
Dice Shard.
Bug!
The D10 can reroll the Suture half of 
Blighted Ovum.
Mr. Maw and 
Gemini's cord dots are considered pieces, each turning into a new monster.
Mask + Heart enemy, and the mask will die instantly.
Attack Fly, 
Swarm, and 
Camillo Jr. enemy can't be rerolled (even though monsters can be rerolled into them).
Stone Grimaces will turn them invisible. They will not fire, but the space they occupied will prevent Isaac from moving through it like an invisible wall.
Dice 
The Binding of Isaac: Rebirth
