Mark VI combat mechanicals were robotic soldiers. The Fleet created 5,000 of them for their wars.
Functionality
They had active phlebotinum armour. The main armament was a plasma-beam rifle built into their right arm. Targeting was aided by a laser rangefinder.
They moved using military-grade tank tracks, could move stealthily or hover using an antigrav engine. They had sensitive audio-detection circuits.
History
The Thirteenth Doctor reprogrammed them, effectively turning them in a peacekeeping force. (PROSE: The Secret in Vault 13)