58 Years Later, Star Trek Has Never Shown The Klingons' Most Terrifying Weapon

The Klingons used a terrifying weapon during their first appearance on Star Trek: The Original Series that has never been shown on screen. Since their debut in TOS season 1, episode 26, "Errand of Mercy," the Klingons have become one of Star Trek's most iconic and recognizable alien species. Several different versions of the Klingons have popped up throughout Star Trek's nearly 60-year history, and their appearance and culture have shifted over time. While Klingons have come to be known as warriors who place a high value on honor, they were not always this way.

In "Errand of Mercy," Captain James T. Kirk (William Shatner) and Mr. Spock (Leonard Nimoy) encounter a group of Klingons led by Commander Kor (John Colicos). The Klingons want control of the strategically located planet of Organia, and the USS Enterprise has been sent to prevent that. While Kirk poses as a local and Spock poses as a Vulcan merchant, the Klingons grow suspicious of the pair's presence on the planet. Kor takes over as the military governor of Organia and employs a weapon known as the mind scanner to interrogate Spock.

Star Trek Never Showed The Klingons’ Mind Scanner In The Original Series

The Device Was Used In "Errand Of Mercy," But Never Shown On-Screen

Although Kor uses the mind scanner to interrogate Spock in "Errand of Mercy," the device is never seen on-screen. The Klingons take Spock to another room to investigate his claims of being a Vulcan merchant. When one of the Klingon officers returns, he informs Kor that Spock's mind is "remarkably disciplined" and that the Vulcan is who he claims to be. When Kirk voices his confusion, Kor explains the mind scanner, saying:

It's a mind-sifter or mind-ripper, depending on how much force is used. We can record every thought, every bit of knowledge in a man's mind. Of course, when that much force is used, the mind is emptied. Permanently, I'm afraid. What's left is more vegetable than human.

Spock later claims that he was only able to withstand the device because his Vulcan "mental disciplines" allow him to maintain a shield around his mind. Kor mentions his mind-scanning device several times throughout "Errand of Mercy," threatening to use it on Kirk, but the episode never actually shows the device on-screen. Since it has its own "examination room," the mind scanner must require a substantial setup, and it has at least four levels of force. Although Spock says the device "reaches directly into the mind," Star Trek never explains exactly how it works.

Why Klingons In Star Trek Never Mentioned Their Mind Scanner Weapon Again

The Klingons Moved Away From Technological Weapons Like The Mind Scanner

The Klingons' mind scanner was never mentioned again after "Errand of Mercy," and there are several likely reasons for this. Firstly, very few elements introduced in Star Trek: The Original Series carried over from one episode to another. The mind scanner, for example, was created for "Errand of Mercy" and was ultimately discarded after it had served its purpose in that episode's plot. Within the Star Trek universe, however, Star Trek: The Next Generation explains why the Klingons stopped using the mind scanner.

Star Trek: The Next Generation reinvented the Klingons as a species, establishing them as a race of warriors who valued honor above all else. A society based on honor would not believe in using torture or weapons like the mind scanner as a way to extract information. Kor himself returned with a new look in Star Trek: Deep Space Nine, further emphasizing how Star Trek had changed the Klingons. Various blades, such as a bat'leth, became Klingons' weapons of choice, and their mind scanner from Star Trek: The Original Series became a thing of the past.