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 species.
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 traveled 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. Fortunately, Odo was unaffected as he was not a humanoid being, and he managed to trick the influenced Julian Bashir into undoing the influence of the spheres by emitting an energy field using the program known as Odo One.
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")