The Robot Guard was put in charge of the keeping the villagers of Dryl working for the Evil Horde in the nearbythe Etherium Mine. He had to make sure the Villagers did not stop working until their cart was full.
When the Etherium ran out, the Robot grew angry and drove the villagers back into the mine. It would have kept it in there forever had She-Ra not arrived on Swift Wind and destroy the Robot.