Karvox

Captain  was the captain on board the Zentra mothership.

When the Zentrabots were sent to take Earth's children hostage, Karvox demanded to at least one of its governments that it would hand its weapons to the Zentra or they would die.

The Eleventh Doctor tracked the Zentrabots' activation signal to the Zentra mothership. While the Doctor was reprogramming a Zentrabot, the Doctor and Danny were captured by a Zentra guard. The Doctor was taken to Karvox, who laughed at his threats to turn the Zentrabots against his own guards. The Doctor sent the signal doing so with his sonic screwdriver and escaped. Karvox angrily demanded his guards to "kill them them all". The Doctor and Danny shook off the guards and successfully returned the children home. (COMIC: The Zentrabot Invasion)