MORRIGAN,OR,MORRIGU

Morgan - (MOHR-gahn) from Welsh mor "sea" or mawr "great, big" + can "bright" or cant "circle" or geni "born." 

Together with Nemain/Babd and Macha
she formed as the Morrigna (Great Queens) a triade.

Modron
the Badhbh Chatha: "Raven of the Battle"
"Washer at the Ford"
"The Red"

An inscription found in France invoking Cathubodva, 
'Battle Raven', shows that a similar concept was known among the Gaulish Celts.According to the "Lebor Gabala Erenn" Morrigu is on of the three daughters of Ernmas, which could be an old fertility-goddess.

At Samhain (30.Oct/1.Nov.), which in my view is basically the festival of Morrigu, Dagda, the King of the Tuatha de Danann, meets Morrigu at a ford and sleeps with her.

The Dagda had a house in Glenn Etin in the north, and he had to meet a woman in Glenn Etin a year from that day, about Samain (Hallowe'en) before the battle. The river Unis of Connacht roars to the south of it. He beheld the woman in Unius in Corann, washing herself, with one of her two feet at Allod Echae (i.e. Echumech) , to the south of the water, and the other at Loscuinn, to the north of the water. Nine loosened tresses were on her head. The Dagda, conversed with her, and they made a union. "The bed of the Couple" is the name of the place thenceforward. The woman that is here mentioned is the Morrigu. Then she told the Dagda that the Fomorians would land at Mag Scetne, and that he should summon Erin's men of art to meet her at the Ford of Unius, and that she would go into Scetne to destroy Indech son of Dea Domnann, the king of the Fomorians and would deprive him of the blood of his heart and the kidneys of his valor. Afterwards she gave two handfuls of that blood to the hosts that were waiting at the Ford of Unius. "Ford of Destruction" became its name, because of that destruction of the king. Then that was done by the wizards, and they chanted spells on the hosts of thE Fomorians.

Through this act he assured that Morrigu would aid the Tuatha de Danann against the Firbolgs in the first battle at Mag Tuired.

Now after the battle has won and corpses cleared away, the Morrigu, daughter of Ernmas, proceeded to proclaim that battle and the mighty victory which had taken place, to the royal heights of Ireland and to its fairy hosts and its chief waters and its river mouths. And hence it is that Badb (i.e.,the Morrigu) also describes high deeds. "Hast thou any tale?" said everyone to her then. And she replied:

Peace up to heaven
Heaven down to earth
Earth under heaven
Strength in every one, etc....
Mythological this act can be interpreted as a reunion of the two major powers: destruction and fertility. After the second battle she foresaw the end of the world and its ruin caused through loss of moral. 
Read the Morrigan-Prophecy

Another tale reports that Morrigu offered her love to CuChulainn, a great irish hero. When he refused to make love with her, she turned into an eels, a female wolfe and a red cow to fight against him and get her revenge. Cuchulainn who fights a monster in a ford at the same time, is able to hurt the eel, to blind the wolfe on one eye and to break the cow one leg, but the fight at two frontiers is too much even for him. When a Caillech, which is in reality the Morrigan herself, comes his way he begs her for a drink of milk from the cow she is holding. The milk helps the hero to regain his strength and he blesses the Caillech and the cow for helping him. This behavior satisfies the Morrigan.

She appeared to the hero Cúchulainn (son of the god Lugh) and offered Her love to him. When he failed to recognize Her and rejected Her, She told him that She would hinder him when he was in battle. When Cúchulainn was eventually killed, She settled on his shoulder in the form of a crow. Cú's misfortune was that he never recognized the feminine power of sovereignty that She offered to him. She appeared to him on at least four occasions and each time he failed to recognize Her.
1. When She appeared to him and declared Her love for him.
2. After he had wounded Her, She appeared to him as an old hag and he offered his blessings to Her, which caused Her to be healed.
3. On his way to his final battle, he saw the Washer at the Ford, who declared that She was "washing the clothes and arms of Cúchulainn, who would soon be dead."
4. When he was forced by three hags (which represent the Morrígan in Her triple aspect) to break a taboo of eating dogflesh.

(from: The Morrígan by Danielle Ní Dhighe)

In the Arthus legend she appears as Morgana le Fay/Morgan. Reduced to the role of a witch and enemy of the christian Arthus (but his half-sister sic!), she still has some of the old attributes of the dark goddess.

As a messenger of death her myth is still alive in the Middle Ages: see f.e. the Kundrie in "Parzival" of Wolfram of Eschenbach