Glowing Hourglass

For the item with a similar name, see The Hourglass.

Glowing Hour Glass is an activated item added in Afterbirth.

Effect

Upon usage, Isaac will be returned to the previous room and everything that happened in the current room will be undone.
- Health, bombs, coins, keys, cards/runes/pills, items, and trinkets will be restored.
- Certain consumables (such as the Joker) do not get restored.
- Score and Time will reset, but about one second will be spent in unskippable animation after use.
- Event counters will get restored (including Donation Machines, Greed Machines, and Eden's Blessing).

Notes

Does not return extra lives.
Using a Joker and then the Glowing Hour Glass to return does not guarantee a Devil Room for every floor as the Joker card does not get refunded. The reason for this is that you immediately change rooms after the Joker card is used, as such reverting to before it was used is impossible.
Does not preserve the Devil Room or Angel Room door if used to return to the boss room.
Does not turn a character back into another should they have been revived by Ankh, Lazarus' Rags, or Judas' Shadow.
- Character changes are reverted by Glowing Hour Glass.

Donations to the Donation Machine or Greed Machine are not reverted, and they can be reset into a working state once jammed.
- Other counters not tied to your specific run, such as Slot Machines or Tinted Rocks destroyed, continue to accumulate, allowing easy unlocking of secrets such as the Counterfeit Penny, the D4, and Conquest if you have access to infinite uses of the Glowing Hour Glass (see below).
- Event counters are rewinded by the Glowing Hour Glass.
With the Curse of the Blind, Glowing Hour Glass can be used to pick up or purchase an unknown item to see what it is, then decide whether or not to undo picking it up.
Using the Glowing Hour Glass to prevent picking the Glowing Hour Glass up while previously having had an active item will return the active item and discharge it completely.
No Damage Achievements are still available if the Glowing Hour Glass is used to reset damage.
Isaac's temporary familiars (blue flies and spiders) duplicate when using the Glowing Hour Glass.
- Fixed.
If combined with The Battery or Sharp Plug while blue spiders are present, this combo can generate an infinite army of blue spiders.
The Retro Vision Pill will continue to affect the game even after using the Glowing Hour Glass.
Can be used to unlock multiple achievements tied to the killing of certain bosses such as Mom's Heart / It Lives.
If there is a battery charge in a shop, the Glowing Hour Glass can be used infinitely, by entering the shop without a charge and using the battery to recharge and exit the shop. This is useful for duplicating temporary familiars or filling up the donation machine, among other uses.
Using the Glowing Hour Glass right after beating Mom's Heart / It Lives / Ultra Greed allows you to get additional Eden tokens.
If a new game is started and Eden begins with this item, using it in the first room will cause the game to crash.

Synergies

? Card - Allows for infinite usage as the ? Card gets refunded upon usage.
- The ? Card doesn't get refunded upon usage.
48 Hour Energy pill - Allows for infinite usage as the pill gets refunded upon use.
The Battery - When the item is double charged and used it will also refund the used extra charge bar, making it possible to use it endlessly.
- The extra charge bar is not refunded.
Bum Friend - Using the Glowing Hour Glass after the Bum Friend has picked up coins but before it has spawned pickups will restore the coins in the room but will still cause the Bum Friend to drop pickups. This can be used to repeatedly generate pickups from the same set of coins.
Curse of the Tower - If used quickly after taking damage, Troll bombs will spawn in the previous room. If you have the Safety Scissors, these can be harvested as normal.
Dark Bum - Using the Glowing Hour Glass after the Dark Bum has picked up hearts but before it has spawned soul hearts will restore the hearts in the room but will still cause the Dark Bum to drop soul hearts. This can be used to repeatedly generate soul hearts from the same set of hearts.
Habit - Allows rooms to be repeated infinitely as long as Isaac has enough health to take two hits, which are refunded on use.
More Options - If used after entering the Treasure Room for the first time, upon reentering the room, one item will have changed places and another will be new, effectively making More Options a choice of 3 items instead of 2. If used a second time, the items change back.
Sharp Plug - Allows for infinite usage as long as you have more than 2 full hearts as the hearts used to charge will be refunded upon use.