The Morrigan's most memorable appearances are in the great Ulster epic, the Tain Bo Cuailnge, in her dealings with the hero Cu Chulainn. She comes to him in the form of a beautiful young woman and offers him her love; when he, intent on battle and not recognising her, refuses, she turns against him, and in the fighting that follows she attacks him in the shapes of an eel, a wolf and a heifer, each time to be wounded by him, a hostility born of the slight. Elsewhere she is the washer at the ford, the terrible figure a warrior sees washing bloodstained armour and weapons in a river before a battle: to see her at her washing is to know that the arms being washed are one's own, and that one is going to die.
In this guise she is the very image of foreknown death. Yet the Morrigan is also bound up with sovereignty and with the fertility of the land: she unites with the Dagda before the Second Battle of Mag Tuired, and afterwards she pronounces a prophecy of peace and plenty and, in the same breath, of the strife and the end of the world to come. She is not simply malevolent; she is the divine embodiment of the terrible and fated dimension of war and kingship, the queen who decides who will fall, who foretells the slaughter, and who wheels over the battlefield in the form of the carrion crow.