An ornate clock of alien design that Benjamin Sisko built compulsively while under telepathic influence, and afterwards kept on display in his office on Deep Space 9.
The clock is a product of the Deep Space Nine episode Dramatis Personae. A telepathic archive left by an extinct Gamma Quadrant people, the Saltah'na, takes hold of the station's senior staff and forces them to re-enact the power struggle that destroyed that civilisation.
Kira plots mutiny, O'Brien becomes a watchful loyalist, and Sisko, cast as the distracted ruler, loses interest in command and withdraws to design and build an elaborate timepiece. Only Odo is unaffected, and he manages to drive the influence out.
With everyone restored, Sisko keeps the finished clock and sets it up in his office. It remains part of the set dressing for the rest of the series.