What Is An Agonizer? Star Trek's Mirror Universe Torture Device, Explained

The "Star Trek" Mirror Universe is full of wonders and dangers, and the torture device known as the Agonizer has long fascinated audiences. 

Designed to inflict intense physical pain on its victims, the Agonizer doesn't actually cause any injuries. In the Mirror Universe, Terran Empire soldiers carry an Agonizer and use it to punish those who commit various offenses. "Star Trek: The Original Series" introduced this handheld device in the Season 2 episode "Mirror Mirror" — the best "Star Trek" Mirror Universe episode of all time, according to fans. In the episode, an alternate version of Spock (Leonard Nimoy) disciplines his crew member, Kyle (John Winston), with an Agonizer. A larger version, known as the Agony Booth, can be observed when Chekov (Walter Koenig) is placed in it after trying and failing to kill one of the best "Star Trek" captains, Captain Kirk (William Shatner), in the Mirror Universe.

Numerous characters are placed in the Agony Booth in "In A Mirror, Darkly" from Season 4 of "Star Trek: Enterprise" — which showcased the torture cell as a new invention at this point in the timeline. The tiny instrument and bigger transparent enclosure's effect on a person appears similar to that of a taser, though the full-body nerve pain stimulated by the Agonizer is much more severe. It next made an appearance in "Star Trek" Season 3, where in "The Day of the Dove," Chekov suffers the same type of Agonizer wielded by a Klingon.

After "Star Trek: The Original Series" in the 1960s, the Agonizer returned on several more occasions to torment characters. "Star Trek: The Next Generation" brought back the concept of excruciating pain without trauma or death in a different, yet arguably more sinister, fashion. "Gambit, Part I" and "Gambit, Part II" in 1993 featured small Agonizer-like implants called neural servos, used by the mercenary Arctus Baran (Richard Lynch) to control his humanoid crew members. 

A more traditional Agonizer didn't re-appear until "Star Trek: Deep Space Nine" three years later. The alternate reality-centric episode, "Shattered Mirror," depicts dystopian torture gadgets close to those in "Star Trek: The Original Series" — though, in this instance, they don't require physical contact with someone's body to function. Regent Worf (Michael Dorn) and Julian Bashir's (Alexander Siddig) Mirror Universe counterparts can be seen intimidating prisoners with an Agonizer in the episode.

Even though the Agonizer hasn't appeared on screen for many years, it remains one of the most intriguing and terrifying technological feats in the "Star Trek" TV franchise.