Fomorians were a group of semi-divine races such as Giants who inhabited Ireland in pre-historic times to the ancient times when they were conquered by the Danu group of Nemedians. The Formorians were constantly warring against invading groups. They may have once been believed to be the beings who preceded the gods, similar to the Greek Titans. Its because of this that Giants were thought to be in the ranks of Formorians. Most likely the Titans the taller giants were defeated by the time the Formorians were defeated.
It has been suggested that they represent the gods of chaos and wild nature, as opposed to the Tuatha Dé Danann and Fir Bolg, who represent the gods of human civilization and virtue. Alternatively, they may represent the gods of a proposed pre-Goidelic population of Ireland.
They are sometimes said to have had the body of a man and the head of a goat, according to an 11th century text in Lebor na hUidre (the Book of the Dun Cow), or to have had one eye, one arm and one leg, but some, for example Elatha, the father of Bres, were very beautiful. Bres himself, for example, carries the epithet "the Beautiful."