The captain of the USS Reliant who was captured and mind-controlled by Khan Noonien Singh, and who killed himself rather than murder Kirk.
Clark Terrell commands the USS Reliant, with Pavel Chekov as his first officer, while it searches for a lifeless planet on which to test the Genesis device. Mistaking Ceti Alpha V for its uninhabited neighbour, Terrell and Chekov beam down and are captured by Khan Noonien Singh.
Khan places Ceti eels in their ears to control them, and they help him seize the Reliant and reach Regula I. Ordered by Khan to kill Kirk, Terrell resists the eel's influence and turns his phaser on himself. He was played by Paul Winfield.