Handbot

Handbots were alien robots designed to aid people with the plague. They administer a medicine called Kindness, which is deadly to anyone alien to them. The Handbots have no face but a blank head. They see using their hand. In times of defence, their heads break apart, to reveal a gun which fires an anaesthetic. When someone speaks to them, they choose whether the statement will be accepted or rejected by the green and red buttons on their chest. (DW: The Girl Who Waited)