The Probert Encyclopaedia of Celtic Mythology

FOMORI

In Celtic mythology, the Fomori are demons that live in the impenetrable darkness of the sea's depths and in lakes and dark pools in the upper world. They were once ruled by Balor, who provided them with victims, but after his death they returned to their waters and prey on people, taking the form of sea-monsters, lake spirits and the boggarts who lurk in the fens.
Research Fomori