In the 23rd century, Doctor Rycho settled on Raylo. He constructed a number of Mortard robots that helped him build an underground complex in a cavern. The robots were powered by life energy absorbed through stasis chambers.
In 2266, the Federation starship USS Enterprise visited Raylo, and James T. Kirk and Spock explored its surface. Rocket drones hypnotized Kirk into entering Rycho's cavern and climbing into a stasis chamber. Spock and Leonard McCoy explored the caverns and discovered Rycho's operations. They were able to capture Rycho, locate Kirk, and free the captured rescue party. (TOS comic: "Rescue at Raylo")