Balok's pilot vessel
From Memory Alpha, the free Star Trek reference.
The pilot vessel of 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.
On Stardate 1514.1, the USS Enterprise was forcefully towed by it and could only free itself under great risks. (TOS: "The Corbomite Maneuver")
