An Algolian keepsake.
A keepsake was an ancient artifact made by Algolian provosts on the planet Algol II. It had temporal properties — it could foretell the future, and in certain situations could provide a means of time travel.
History and specifics
Keepsakes were fashioned ten thousand years ago. They were small, clear spheres infused with water from the Well of Tomorrows. This water contained tachyons, which gave a keepsake the ability to present images of a person's future to whomever held it. Several keepsakes were excavated by archeologists in the remains of the city of Ithahulan.
In 2254, J. Mia Colt and José Tyler studied a keepsake. When Tyler touched it, he saw himself in command of a Federation starship decades in the future. Colt saw nothing when she touched it. However, emissions from her tricorder activated tachyons in the water, propelling her through time to the year 2293. She arrived on Earth in an alternate reality whose history had diverged after her disappearance. (EV comics: "Futures, Part One", "Future Tense, Part Two")
With the aid of James T. Kirk and Christopher Pike, she was returned to Algol, now a holding of the Klingon Empire. A landing party located the Well of Tomorrows, which returned her back where her journey began, aboard her USS Enterprise in the prime reality 2254.
When Captain Christopher Pike touched the keepsake, it revealed how he would appear in 2267. (EV comic: "Now and Then")
