The pilot vessel used by Balok was a small ship capable of enormous power. It controlled the flagship Fesarius and was equipped with a tractor beam. Besides Balok, no crew was needed.
After threatening Balok with the Corbomite, he decided to send the Fesarius away, and tow the Enterprise to a First Federation planet using a pilot ship. The Enterprise, observing that the engines of the alien ship were overstretched, tried to pull away, and succeeded. The pilot vessel stopped, and sent an emergency broadcast requesting help, as its engines overloaded. An away team transported on to the vessel, just to find Balok waiting for them.