A transparent chamber used aboard starships of the mirror universe to punish crew members by subjecting them to prolonged and intense pain.
The agony booth is first seen in the episode Mirror, Mirror. Aboard the ISS Enterprise, Chekov tries to assassinate Captain Kirk in order to rise in rank; when one of his own men betrays him he is taken to the booth, where he is seen writhing behind the glass.
The booth is the harsher counterpart of the hand-held agonizer that every crew member carries, and is reserved for serious offences. The mirror Spock makes plain that a sentence there can last a long time.
The Enterprise two-parter In a Mirror, Darkly shows its origin a century earlier. It is credited to Doctor Phlox and Major Reed of the ISS Enterprise NX-01, who designed it to keep stimulating different pain centres so that the victim never grows used to it.