Saline drone

A saline drone was a miniature robot that absorbed moisture, preferably ionic compounds, from other creatures and used them to replenish its host. They looked like flying, blinking lights.

Saline drones attacked Daphne Garsington in a Mesopotamian tomb in the 1920s and drained her of all her bodily fluids. River Song and Bertie Potts later entered the tomb and escaped the drones. (AUDIO: The Boundless Sea)