Saltah'na energy spheres
The Saltah'na energy spheres were the creation of the Saltah'na and were used by them to preserve their essence before an internal power struggle destroyed that ancient race.
The spheres had the ability to merge with the conscious personality of certain humanoid species, causing the personalities of the most prominent members of the original power struggle to emerge and eventually supplant the personalities of the individual who came into contact with the sphere. This had the additional effect of causing that individual, and those around him, to re-enact the disastrous events that destroyed the Saltah'na.
In 2369 the Klingon starship IKS Toh'Kaht travelled to the Gamma Quadrant and encountered the spheres and fell under their influence, which it then transferred to Deep Space 9 shortly before the ship's destruction. The crew of that station began to re-enact the Saltah'na struggle all over again before finally managing to undo the influence of the spheres.
Benjamin Sisko, whose personality was supplanted by the deposed ruler of the Saltah'na, constructed a clock of unknown design while under the influence of the spheres. He kept the clock after the influence of the spheres was cast off and displayed it in his office. (DS9: "Dramatis Personae")