Clam drones

Clam drones are drones build by the Thals during the Thousand Year War against the Kaleds on Skaro.

Their function was to pick up any enemies on the ground that the bombs from the Thals' planes didn't hit. The soldier Kanzo was warned by his comrade that some drones were only two miles away, but told him that he would catch up. (TV: The Magician's Apprentice)