Hundreds of years ago, the ancestors of Caeminon's inhabitants lived on the surface; they were driven into underground shelters when the war machine their scientists had built went out of control and began killing them. They established a new civilization in which all weapons were banned.
In 2267, the people of Caeminon detected the destruction of the machine and sent an expeditionary force led by Kyr Nostrand to the surface to see if it could be made livable again. They were attacked by vegetable metalloids, the creations of the machine's mind module, and all were killed except Rhuna, who fled. She was rescued by a landing party from the USS Enterprise led by Captain James T. Kirk, and took them to Caeminon in the hopes of finding a way to get them back to their own universe. When the vegetable creatures broke into the city and began attacking the citizens, the Enterprise officers helped fight them off until Kirk realized that the mind module controlling them was part of Rhuna's bracelet and shot it with his phaser, disrupting it and ending the battle, saving Caeminon. (TOS comic: "Siege in Superspace")