This small black hourglass is filled with small grains of a neon green substance at the bottom. The substance appears almost liquid but does not flow to the other bulb when inverted. If illuminated by a detect magic spell, the hourglass gives off the golden aura of Transmutation.

The history and precise origins of this powerful magical item is unclear. It could have been crafted from the fallen branches of the Grandfather Tree, enchanted under the guidance of a Gynosphinx, connected to a dunemantic experiment, or even designed by Primus - the immortal ruler of Mechanus. Most likely though, there is an eldricht source to this strange world-changing power.

Charges. The Hourglass of Time-Well Spent has 1d12 charges when discovered. The specific number of uses remaining is known only to the DM. An Investigation or Perception check only reveals that a portion of the substance has flowed to the top. When the item runs out of uses it is destroyed. It is otherwise invulnerable to damage or magic.

Once per long rest, when a creature attuned to this item has its hit points reduced to zero and is knocked unconscious, the sands of time begin to flow in reverse in the area around them. The continue to make death saving throws as usual, but on a success they can instead choose to spend their time differently. The closest 1d4 living creatures, including the user, return to the same moment 1d4 minutes in the past with their memories of this possible future. No other creatures (including other PC's) retain any knowledge of this potential future. 

Madness of Time. The experience of traveling to a previous moment of possibility is disconcerting and potentially maddening. Each creature transported this way must make a DC 18 Wisdom saving throw to overcome a damaged mind. On a failed save, the creature becomes afflicted with a random form of long-term madness for 1d10 × 10 hours. (See "Madness" in the Dungeon Master's Guide.) A failure of more than 10 also results in a form of short-term madness for 1d10 minutes. The DC increases by 1 each time these creatures are affected by this magic item.

Bent Time. Manipulating time has lasting effects on an area. After the creature has caught up to the moment the item was used, a dunamantic or reality-bending effect of the DM's choosing emanates from the area where it was activated. Each use of this item increases the size of the total effected area by 1. The Twisted Reality Table provides a sample of possible effects, but the DM is encouraged to develop their own.

Twisted Reality Table

Area of Effect