I promised that I would do a write-up on Irish mythology today, and I bring you gifts! As
vovat suggested, I'm going to discuss the Morrigan, a triple goddess from Irish mythology and legends. The information comes directly cited from Katharine M. Briggs' An Encyclopedia of Fairies: Hobgoblins, Brownies, Bogies, and Other Supernatural Creatures (Pantheon, 1976).
Morrigan (moreeghan), or Morrigu. One of the forms taken by the ancient Irish war goddess BADB. In the CUCHULAIN epic, Tain Bo Cuailnge, in which the great war between the FOMORIANS and the TUATHA DE DANANN is celebrated, the three war goddesses in the form of crows are NEMAN, MACHA and Morrigu, of whom Morrigu is the greatest. As Evans Wentz [my note: in The Fairy-Faith in Celtic Countries] analyses the legend, they are the tripartite form of 'Badb'. Neman confounds the armies of the enemy, so that allies wage mistaken war against each other, Macha revels in indiscriminate slaughter, but it was Morrigu who infused supernatural strength and courage into Cuchulain, so that he won the war for the Tuatha de Danann, the forces of goodness and light, and conquered the dark Fomorians, just as the Olympic gods conquered the Titans.
Now, Irish mythology wasn't Briggs' strong point, so I'll give her some credit for what she wrote. However, even though Cuchulain fought in the Tain, he didn't fight for the Tuatha, he fought for the people of Ulster. The hero that the Morrigan gave strength to in The Book of Invasions (which Briggs calls The Book of Conquests), though, was Lugh, the champion of the Tuatha, who did fight the Fomorians. Everything else about the Morrigan she mentioned is pretty accurate. Here's more on the other forms of the Morrigan/Badb:
Neman, or Neamhan. The ancient Irish war goddess BADB took a triple form, Neman, MORRIGU and MACHA, all in the shape of royston or hoodie crows, a form taken in modern irish fairy-lore by the BEAN-SIDHE [my note: banshee]. Each manifestation has a different function and Neman is 'the confounder of armies'. It is she who causes bands of the same army to fight together, mistaking each other for the enemy. Evans Wentz, in The Fairy-Faith in Celtic Countries (pp. 302-7), gives a useful account of these war spirits, founded mainly on Silva Gadelica and The Book of Conquests, but with other comparisons and references.
Macha (ma-cha). One of the triple forms taken by the ancient Irish war goddess BADB. All are in the shape of Royston or hoodie crows. Macha is a fairy that 'riots and revels among the slain', as Evans Wentz puts it in his analysis of Badb's triple form.
Badb, or Badhbh (bibe). The Celtic goddess of war, who, according to Evans Wentz in The Fairy-Faith in Celtic Countries (pp. 302-5), incorporated the three goddesses NEMAN, MACHA and MORRIGU in a single form, that of a Royston or hoodie crow. The mythology has declined into folklore, and a crow perching on a house is often the form taken by the BANSHEE or 'fairy woman'. The narrative of the battle of Moytura [my note: Irish Gaelic, Magh Tuireadh] in The Book of Leinster gives one of the most vivid descriptions of the activities of Badb and her attendant spirits.
A Royston or Hoodie Crow.