Fuath

The  were a species of cephalopod-like, tentacled creatures that lived in water and fed on hate and fear. They appeared in Scottish myths and legends as water demons, and one Fuath dwelled near the shore of Moray, taking babies from the women of the kingdom, and seemingly replacing them with its own mouthless, noseless changeling children.

The Fuath was eventually driven out through the combined efforts of the Ninth Doctor, Queen Gruach, King Macbeth and their son Lulach. Its life was spared by Gruach, who wanted it to live on as a reminder to the people of Scotland not to live in fear. (AUDIO: The Curse of Lady Macbeth)