The item consists on what time-attuned emerald, split in two and assembled around a small clockwork device. When the upper part is turned back, the attuned creature is brought back in time. This can have the following uses:

• When you fail a saving throw, you can revert time to reroll the saving throw. You must use the new result.
• At the end of your turn, you can turn the stone to revert time back to before your turn started, undoing any effects.

You must have your hands free to turn the gemstone to use the item, and the item can't be used again until after next dawn.