Ruk was an android built on Exo III half a million years before the 23rd century by the Old Ones. Ruk was tall, broad and immensely strong, capable of lifting a Human male easily with one hand. Despite his size, he could move silently and gracefully, making him an extremely dangerous physical opponent. He could duplicate voices effortlessly – his actual voice was very low-pitched and gravelly. He was discovered in the underground ruins of that planet in 2261, by Dr. Roger Korby, where he was still tending the machinery the Old Ones had left behind. Even he did not remember how many centuries he had been doing this work. Ruk helped Korby learn how to use the ancient machinery, including the android duplicator. With Ruk's help, Korby built other androids, including Brown and Andrea. In 2266, Captain James T. Kirk and Christine Chapel arrived at Exo III in search of Korby. By then, Korby had reprogrammed Ruk to serve him, and had devised a scheme to infiltrate android duplicates into society slowly and carefully. As part of that scheme, Korby and Ruk imprisoned Kirk and Chapel, and built a duplicate of Kirk to take control of the USS Enterprise. Instinct: