Mirrored World

The Mirrored World is a special area of the Downpour II and Dross II. The layout of The Mirrored World is the exact same as the normal floor, except mirrored left to right. Each room contains the same enemy encounters and has the same block layout, although some rocks may be different. The Treasure Room of the Mirrored World contains Knife Piece 1. The boss is also identical, and, if defeated, will drop an item from the Boss item pool.

Accessing the Mirrored World

In Downpour II or Dross II, there will be a room with a mirror on the side of a wall. In another part of the map, there will be an inextinguishable White Fire Place. Touching the fire will cause the player to "die" and take control of The Lost. This state allows Isaac to pass through the mirror and access the Mirrored World.

Notes

The Mirrored World is covered in a shimmery overlay, and its graphics slowly warp. Additionally, items and pickups will have their artwork inverted, and an alternate reversed version of the soundtrack is played.
Breaking the mirror is possible with a Bomb, and will cut off access to the Mirrored World.
- Breaking the mirror while inside the Mirrored World will cut off access back to the normal world. Isaac will begin to fade and eventually start taking damage. Extra lives cannot be used to prevent death after this, as Isaac will continue dying after using an extra life.
- The mirror will also break if Soul of Cain is used in the mirror's room.
- Sulfuric Acid or Terra can break the mirror.
- Mama Mega! will break the mirror upon entering the room.
On XL floors, only one of the Treasure Rooms will contain Knife Piece 1 - the other will be empty. Both Boss Rooms will drop an item as normal.
All Secret Rooms, Shops, and Vaults will be devoid of items. However, Shopkeeper will still appear, and can drop items as normal.
- The Member Card trapdoor will appear in the shop, and will lead to a store.
- D7 will spawn rerolled versions of whatever was initially in the room in the normal world; that includes any pickups, chests, and pedestal items.
- Using the Shop Restock Machine in the shop in the Mirrored world will make items appear in the mirrored shop. The normal shop will not be rerolled, and subsequent rerolls will not match those of the mirrored shop.
If the location of a secret room or super secret room was first discovered in the mirror world, its location will be mapped when returning to the normal world, and vice versa.
Trapdoors will not be spawned, except to crawlspaces or Black Markets – which will have no items but can be populated with a Shop Restock Machine to spawn some.
Wraiths will appear visible, but they will lack reflections unlike other entities, opposite of their normal appearance.
The rooms in the Mirrored World count as separate rooms, so anything that happens in the normal world room will not affect the mirror world variant of the room, and they drop their own pickups upon completion.
- Using a Joker card in the mirrored world is not recommended, as it will teleport Isaac to an empty version of the Devil Room or the Angel Room, causing the card to be wasted.
The Lost and Tainted Lost can pass through the mirror normally.
- Tainted Jacob can enter the mirror if he has been touched by Dark Esau.
- Tainted Soul can also enter the mirror without a white fire, and in turn, keep his health bar.
  - Even though Tainted Soul can enter the mirror, The Soul cannot.
If a Planetarium or a Library exists in the normal world, it will exist in the mirrored world and require a key to open, even if it's opened in the normal world. However, there will be no items.
To turn back into the original character, it's required to clear 1 room as The Lost. If Isaac is in the Mirrored world, he will turn back after going through the mirror if he has not gone through it already. If there are no rooms left on the current floor, he could clear a room on the next floor and turn back.
Any means of spending blood, including Blood Donation Machines, Devil Beggars, and Hell Game, will result in an immediate death, even if the non-mirrored character has health to spend.
When using any revival items while in the Mirrored World, such as Dead Cat or Judas' Shadow, Isaac's health will still be affected by the revival item used, even though the character in the Mirrored World is the Lost. For example, dying with Dead Cat will set the character's health to 1 red heart, regardless of the player's health in the non-Mirrored World.
The mirror cannot be entered if the player uses Dad's Key or Get out of Jail Free Card.
A Dice Room in the mirror world is distinct from the other Dice Room, is activated separately, and may have a different number.
In co-op mode, or when playing as Jacob and Esau, it is possible to have all but one character in their normal forms (normal health, etc.) while in the mirror world – that one only must touch the flame then use the mirror. Tainted Lazarus only needs one of his forms to become The Lost, while the other (flipped) form can stay normal in the mirror world.
Items and trinkets that affect tear projectile direction, such as Ouroboros Worm, will be mirrored horizontally from Isaac.

Bugs

Bug!	Spawning items with a Restock Machine in a Member Card mirrored shop will result in them overlapping with the items in the non-mirrored Member Card shop.